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Introduction to Wetland Plants

Our understanding of the ecology of wetland plants has increased dramatically over the past several decades. Much of this understanding has been fueled by the surge of interest in wetland ecosystems more generally. Research has documented the high levels of biological diversity that wetlands support as well as the unique ecological processes, or functions, that occur there. As information on wetlands has increased, so too has the literature on wetland plants field guides and manuals have been completed for many geographical areas, numerous magazines and scholarly journals are devoted solely to their study, and a growing horticultural and aquarium trade is based on their cultivation and sale. The use of wetland plants in the delineation of wetlands in the U.S., as well as the relatively new field of wetland restoration, has created a demand for people knowledgeable in their taxonomy and ecology. In addition, concern about the invasive potential of some species, such as Eichhornia...

Integration of pollination and mating

Lloyd's mating-system models consistently predicted either exclusive outcrossing or complete selfing, which contrasted with a growing body of evidence that many plants produce mixtures of selfed and outcrossed seeds (Barrett and Eckert 1990 Goodwillie et al. 2005). Although Lloyd (1992a) was aware of several genetic models that predicted mixed mating, he doubted whether the proposed mechanisms could explain its prevalence, given the restricted conditions that they required. In the absence of a general functional explanation, Lloyd concluded that mixed mating generally resulted from combinations of the inevitability of geitonogamy for plants that display multiple flowers simultaneously, and the advantages of reproductive assurance in the face of insufficient pollen dispersal. In contrast, more recent theoretical analysis have identified factors that may select for mixed mating even when seed production is not pollen limited (Goodwillie et al. 2005 Chapter 4). topic by forcing...

Early investigations of plant sexual diversity

In long-lived species for which repeated episodes of reproduction magnify differential costs. Their major review of this topic (Lloyd and Webb 1977), which today is Lloyd's most cited publication, documented differences between the sexes and highlighted how their distinct roles in sexual reproduction influence the evolution of sex ratios. Lloyd also became interested in the mechanisms responsible for female-biased sex ratios, which are reported less often (Lloyd 1974b). In this paper he effectively disposed of previous group-selection arguments based on maximizing seed production at the population level and argued that the common occurrence of female bias in species with sex chromosomes could result from differential fertilization of ovules by female- versus male-determining gametophytes as a consequence of the genetic differentiation of sex chromosomes. This interesting idea has some support, although the mechan-ism(s) responsible are still unclear (Conn and Blum 1981 Stehlik and...

Gender concepts and theory

In which oi and pi are the numbers of ovules and pollen grains produced by individual i, respectively, and E is the ratio of ovules to pollen grains in the population as a whole. Therefore, pheno-typic gender considers the production of pollen and ovules (or seeds) of individual plants relative to the average ratio of expenditure in the population. Note that Lloyd (1979b, 1980b, c) originally referred to Gp as functional gender, but changed terminology in his 1984 review with K. S. Bawa to that given in eq. 1 and 2. Values of Gp can range from 0 to 1, denoting in the extremes strictly male and female plants, respectively (Fig. 1.3c). Gp has now been measured to describe gender strategies in a wide range of flowering plants (e.g., Fig. 1.3 also see Thomson and Barrett 1981 Lloyd and Bawa 1984 Wolfe and Shmida 1997 Vaughton and Ramsey 2002). However, truly functional measurement of gender based on mating success using genetic markers is still in its infancy (Elle and Meagher 2000 Morgan...

Evolution by Alien Species and Global Change

Global change compounds the evolutionary pressures acting on invading aliens.Where communities are in disequilibrium, natural selection is likely to favor plants and animals with short life spans, high dispersal abilities, rapid population growth capacities, opportunistic patterns of resource use, and high evolutionary adaptability (Barrett 2000). Fragmentation of habitats is likely to favor species with high dispersal and colonization capabilities (Barrett 2000).Thus, increasing numbers of rapidly evolving alien species are likely to alter the composition and dynamics of all of the world's ecosystems.

The evolution of heterostyly

Heterostyly and several prominent evolutionary biologists from the U.K. (e.g., R. A. Fisher, J. B. S. Haldane, K. Mather, D. Lewis, B. Charlesworth, and D. Charlesworth) had worked on these floral polymorphisms. However, questions remained concerning the evolution of heterostyly. It did not escape Lloyd's attention that unlike his research on gender strategies, which are exceptionally well represented in the New Zealand flora, he was now studying a problem for which there were no representative species native to New Zealand (Godley 1979). Perhaps this was an advantage, as it enabled him to approach heterostyly in a fresh way, unencumbered by the details of a particular group, such as Primula on which much previous literature was concentrated (reviewed in Richards 1997). However, Lloyd did study heterostyly outside of New Zealand and his interest in Narcissus took him to the Iberian Peninusla in 1990 (Fig. 1.1d) in an effort to settle a long-standing controversy concerning the nature...

Two Important Distinctions

(2) were isolated from one another by an essentially inhospitable matrix that was hostile to a majority of organisms (Haila, 2002) and (3) movement of biota often depended on corridors or long-distance dispersal movement to move between patches (Saunders et al., 1991 McIntyre and Barrett, 1992). This schematic view led to the description of landscapes in terms of patches (usually homogeneous), corridors (usually linear), and matrix (the most connected part of the landscape (Forman, 1995 McIntyre andHobbs, 1999). Of course, depending upon the degree of disturbance, the matrix can be original habitat or the disturbed area. Observations in Australia in the early 1990s led McIntyre and Barrett (1992) to suggest that the schematic view of landscape did not apply to systems heavily modified by agriculture. They observed that the intervening areas were modified versions of the original habitat and were not totally inhospitable to movement animals moved through these areas. This was a...

Cropland Weed Adaptation for Dispersal by Humans

Many cropland weeds have capitalized on dispersal as crop seed contam-inants.These species have evolved races that show patterns of growth and reproduction that mimic those of crop plants (Barrett 1983).These forms, known as agroecotypes, are largely restricted to stands of cultivated crops. Agroecotypes are often weedy races of the crop plant itself, with the Perhaps the most remarkable set of agroecotypes is that associated with rice (Barrett 1983). Some of these are wild relatives and weedy races of cultivated rice (Oryza sativa). Others are races of barnyard grass (Echinochloa crus-galli) that have evolved to mimic the phenology, vegetative appearance, and seed morphology of cultivated rice. Two chromosome races of E. crus-galli the tetraploid race, phylopogon, and the hexa-ploid race, oryzoides are worldwide in distribution in areas where irrigated rice is grown. These races are essentially restricted to rice fields, although other forms of E. crus-galli occur as weeds outside...

Variable pollination environments

Essential components of plant reproduction (e.g., Barrett et al. 1989 Fausto et al. 2001 Thompson 2005 Chapters 8,12,15 and 16). Theoretical studies are beginning to include variable pollination environments explicitly (e.g., Pannell and Barrett 1998 Nuismer et al. 2003 Chapter 12).

Human Capital at the Firm Level

We know of no published, empirical evidence of the benefits of biochemical discoveries filtering down to the poorer segments of host communities. If that conjecture is true, then to a first-order approximation, the opportunity cost of habitat conversion does not change among the poor. Then the pressure to convert habitat remains among the poorer subpopulations in communities in or surrounding biodiverse areas. If the poor are among the principal agents (as well as victims) of tropical ecological degradation (Barrett 1996), bio-prospecting then fails to alter the incentives of those whose behaviors most need to be changed (Barrett and Lybert 2000 297).

Implications of Selfcompatibility for the Invasion

The ability to self is advantageous for successful colonization following long-distance dispersal of a single propagule, because there is no need to wait for a sexual partner (Baker's law Baker, 1955). Once a plant has successfully established, selfing transmits proved genes of a plant, which was able to survive at that site. Nevertheless, theoretical models suggest that an optimal mating system for a sexually reproducing invader in a heterogeneous landscape is to be able to modify selfing rates according to local conditions. In early stages of invasions, when populations are small, plants should self to maximize fertility. Later, when populations are large and pollinators and or mates are not limiting, outcrossing is more beneficial because it generates increased genetic polymorphism (Pannell and Barrett, 1998 Rejmanek et al., 2005).

From Ganesha to the present

Although a shadow of its former glory, the Sultanate managed to survive for over a century, first under the Sayyids, nominees of Timur, and later under the Lodis. Ibrahim Lodi, the last of this line, fielded about 100 elephants (one exaggerated report mentions 1,000) at the battle of Panipat (a.d. 1526), where he was killed by Babur, the founder of the Mughal dynasty. The latter used firearms, possibly the first instance of their use in the subcontinent.

Underwater photography

Underwater photography has become an increasingly important tool for diving marine scientists over the past 15 years or so. Diver-held underwater cameras fall into two main categories standard 35mm land cameras and flashguns enclosed in pressure-proof housings and amphibious, waterproof cameras with dedicated flash guns of which the Nikonas system is the most widely used (Figure 3.32). Both systems can be fitted with a variety of wide-angle and close-up lenses. Housed cameras tend to be bulky but have the inherent capabilities of any single lens reflex camera allowing automatic exposure and focusing. Several amphibious cameras now have automatic exposure capability with through-the-lens (TTL) metering but to date, only one, the Nikonas VI, has automatic focusing. The high price of this model puts it beyond the reach of many divers.

Underwater television and video

Television cameras can be mounted on towed underwater sledges along with still cameras. The television signals give a continuous record of the strip of sea bottom traversed by the sledge, and colour photographs show greater detail of particular areas (Holme and Barrett, 1977). If the distance travelled by the sledge is measured, then quantitative estimates of fauna can be made.

Discussion and conclusion

In developing this theory, I assumed obligate outcrossing. In contrast, hermaphrodites commonly self-fertilize, spanning the whole range from complete outcrossing to complete selfing (Barrett et al. 1997 Goodwillie et al. 2005). As Zhang (2000) showed, reproductive effort often correlates positively with increased selfing rate, because self-fertilization increases the genetic value of offspring from the standpoint of an invading allele that affects the selfing rate. Selfed progeny might contain two copies of the invading allele, whereas outcrossed progeny can contain only a single copy. Thus, selfing increases female fitness gains, which in turn select for both higher female allocation and higher total reproductive effort (Zhang 2000). However, the positive correlation between selfing rate and reproductive effort has yet to be demonstrated empirically. Furthermore, higher selfing in large plants with many flowers will also select for increased femaleness with plant size (de Jong et...

Harmonic Mean Distribution

Human population densities fall in an inverse harmonic mean fashion from centers of urban areas through rural areas. Consequently, Dixon and Chapman (1980) proposed using a harmonic mean distribution to describe animal home ranges. Contours for a utility distribution are developed from the harmonic mean distance from each animal location to each point on a superimposed grid. The harmonic mean estimator may accurately show multiple centers of activity, but each estimated utility distribution is unique to the position and spacing of the underlying grid. Spencer and Barrett (1984) modified the method to reduce the problem of grid placement but a large problem with grid size remains. When a very fine grid is used, the resulting utility distribution becomes a series of sharp peaks at each animal location. When a coarse grid is used, the utility distribution lacks local detail and is overly smoothed. For many data sets, the harmonic mean estimator actually appears both to exaggerate peaks...

Social Play as a Tension Reduction Tactic

Henzi and Barrett (1999), Loizos (1967), Merrick (1977), and Goodall (1968) emphasized the similarity shared by social play and grooming. In fact, both behaviors entail close physical contact for long periods and have an important role in social cohesion. Grooming maintains social stability by reducing tension and providing appeasement during contexts characterized by conflict of interest (Aureli et al. 2002, Merrick 1977, Schino et al. 1988). Social primates use diverse strategies to mitigate tension and to prevent conflict escalation such as communicative displays, dominance relationships, and greeting gestures (Preuschoft and van Schaik 2000, Whitham and Maestripieri 2003).

The return of the Beagle to the Foundations of Origin 183744

The point about CD, though, is not any of this, but that he discovered *natural selection. His post-Beagle *notebooks, now available in their entirety (Barrett etal. 1987), make clear that this discovery happened in the autumn of 1838,withvarious scholars even venturing specific dates.

Site Attribute Design

1993 Loeb 1993 Nadeau et al. 1995), wintering areas (Nixon et al. 1988), or areas recolonized by an expanding population (Hacker and Coblentz 1993). Other studies have compared habitat characteristics of randomly located sites to sites where birds or mammals were observed, radiolocated, or known to have been from remaining sign (Dunn and Braun 1986 Krausman and Leopold 1986 Beier and Barrett 1987 Edge et al. 1987 Lehmkuhl and Raphael 1993 Flores and Eddleman 1995).

Population Age and Size

Other species have a limited ability to spread vegetatively between resource units and individual mycelia do not frequently extend outside, for example, a single tree. This was the case for Phaeolous schweinitzii (Childs, 1937 Barrett and Uscuplic, 1971), and Collybia fusipes (Marcais et al., 1998). Inside the bole of a single tree, several genets of Phellinus tremulae were detected, indicating multiple establishments by basidiospores (Holmer et al., 1994). Another interesting case of interspecific competition was observed in Douglas fir (Pseudotsuga mensiezii). Adams and Roth (1969) reported on a population structure of Fomitopsis cajanderi where several genets were present at the site of entrance into the broken tree stems while further down the stem only a few genotypes had expanded at the expense of the others. Typically, multiple spore infections will give rise to small populations of up to tens of decay mycelia in dead stems of conifers (Norden, 1997 Hogberg et al., 1999...

Evolutionary biology of the paternity shadow

Floral variation among flowering plants has been studied extensively (Lloyd and Barrett 1996 Barrett 2002). Traditionally, many floral traits in hermaphroditic plants have been interpreted as anti-selfing mechanisms that safeguard maternal function, but more recent work recognizes their importance in also promoting pollen dispersal and paternal function (Barrett 2002). The paternity shadow amalgamates these perspectives, because

Advantages and Problems of the Demographic Response Design

Reproduction and survival data may be more apt to reflect real influences of habitat on demographics. However, reproduction and survival are probably also tied to habitat in a complex manner. For example, a number of studies observed a direct relationship between cover and the survival (and thus density) of voles (Microtus spp.), but a lower threshold exists below which reductions in cover have little effect on vole density above the threshold, survival and density increase but eventually reach an upper asymptote (Birney et al. 1976 Adler and Wilson 1989 Peles and Barrett 1996 figure 4.2C). The vole studies found that cover provides food as well as protection from predators, and also may affect microclimate, activity patterns, and interactions among conspecifics, all of which affect the cover density relationship. Moreover, male and female voles have different responses to varying cover (Ostfeld et al. 1985 Ostfeld and Klosterman 1986), and cover demographic relationships tend to be...

Gross Mycelial Contact

Figure 3 Effect of the wood decay fungus Phanerochaete velutina, growing from a piece of wood (PV), on allocation of carbon to the extra-radical mycelium of the Mycorrhizal fungus Paxillus involutus growing in association with Betula pendula (a and b), and on Suillus bovinus in association with Pinus sylvestris in soil microcosms (d and f). (a) and (b) show ectomycorrhizal mycelial growth in the absence of the saprotroph. Plants were pulse-labelled with 14C, and this was quantified in a 20 x 24 cm below-ground area by digital autoradiography (indicated by a white line in b). Autoradiographs are shown in (b), (e) and (f) with the radioactivity scale indicated in (b). In the interaction with P. involutus there were two patches of litter (L) in the microcosm to provide resources for the EM fungus. Note the truncation and browning of the P. velutina cords in contact with P. involutus (small arrow heads) and the deflection of the growth of the saprotroph on the right of the wood block...

Hypk King Saug Cem Huds Hudn Rav

1988 Carter, Rybicki, and Hammerschlag, 1991 Barrett and Findlay, 1993) suggesting these plants may be significant in river-scale primary productivity. For instance, continuous measurements of dissolved oxygen in several SAV beds shows that these sites are super-saturated with oxygen approximately 30 percent of the time and O2 concentrations can be as high as 150 percent of saturation (Fig. 17.3). Recent modelling efforts based on photosynthesis-irradiance relationships for both phytoplankton and submersed plants show that oxygen production by SAVis a large component of midsummer oxygen budgets (see Cole and Caraco, chapter 9, this volume). The relative importance of submersed macrophytes as primary producers has increased dramatically since the zebra mussel invasion (1992). Prior to 1992, SAVNet Primary Production (NPP) and Gross Primary Production (GPP) were roughly 10 percent of phytoplankton NPP and GPP. Since the zebra mussels (see chapter by Strayer) have dramatically depressed...

Selection versus drift in speciation

The 'neutral expectation' for rates of speciation due to stochastic processes alone is not well-defined (although see Barton 1996) in principle, however, accelerated diversification in angiosperms could be consistent with increased susceptibility to reproductive isolation via stochastic forces (e.g., founder events, bottlenecks, and or inbreeding). The relative importance of drift and selection is presently debated both theoretically (e.g., Turelli et al. 2001) and with respect to observed empirical patterns. For example, it has frequently been suggested that stochastic forces play a large role in diversification processes on islands (e.g., Barrett 1996 Weller et al. 2001), although novel selective environments might also account for island diversification (e.g., Barton 1996).

General effects of disturbance and their reproductive consequences

To characterize the consequences of different disturbance types on pollination and plant reproduction we constructed five matrices, which relate the direct and indirect qualitative effects of disturbance on plant populations as depicted in Fig. 9.1. The first two matrices identify direct effects of disturbance types on plant and pollinator attributes, although we also acknowledge the indirect effects of disturbance on pollinator attributes mediated by changes in plant attributes. The next two matrices relate the effects of the modified plant and pollinator attributes on different aspects of stigmatic pollen deposition, which also mirror aspects of pollen export and thus of male function (e.g., Harder and Barrett 1995 Chapter 4). Finally, the fifth matrix relates pollination success to reproductive output. Each matrix cell contains a symbol indicating the currently understood effect of a row factor or attribute on a column factor or attribute. These symbols include , a positive...

Relation of pollination to modified plant attributes

Increased floral display or nectar production may enhance pollen removal and deposition by increasing pollinator attraction to attractive and rewarding plants. However, these traits may also increase self-pollination and pollen discounting by increasing the number of flowers visited per plant by individual pollinators (geitonogamy) and, in the case of nectar, the time that each pollinator spends visiting individual flowers (autogamy) (Harder and Barrett 1995 Eckert 2000). Thus, whereas these individual-level attributes may initially enhance both pollination quantity and quality by increasing pollinator attraction, they may eventually decrease pollination quality through the transfer of self-pollen while still increasing pollen deposition (Table 9.3).

Ecological Effects of Hunting

The ecological effects of hunting are no less diverse than its history. While hunters act as apex predators in ecological terms, human hunters rarely conform to the assumptions of the Lotka-Volterra equations (predator-prey equations). Human hunters can and often have operated as keystone predators, exerting a disproportionate effect on prey populations relative to human numbers. The ecological effects of modern hunting, however, are mediated by governmental regulations. Throughout much of the twentieth century, the maximum sustainable yield paradigm guided hunting regulations. During the latter half of the twentieth century fixed harvest quotas based on maximum sustainable yield decimated many global fisheries and whale populations. This failure led to regulation of hunting effort (season timing and length, bag limits, means methods (archery vs. firearms)). Such regulations control harvest indirectly by altering hunting effort and hunter efficiency. Because hunter effort

Ecological Effects on Hunting

While technology (e.g., firearms, motor vehicles) has allowed modern hunting to develop independent of ecological relationships in some ways, ecosystems have shaped the social nature of hunting. In relatively open landscapes, persistence hunting (using teamwork to run down prey) evolved. In densely forested areas, hunting evolved to be less of a group activity. Attributes of prey also influenced the social nature of hunting. Large prey species required larger groups of hunters, processors, and eaters. Even with modern technology, however, ecosystems influence the social dynamics of hunting. Emerging zoonotic diseases are shaping perceptions of hunting risk and influencing hunting participation. When chronic wasting disease (CWD) was discovered in Wisconsin (USA) deer herds in 2002, hunter numbers began declining and more than 50 of deer hunters using firearms that hunted in 2001, but not 2002, cited CWD as their reason for not hunting.

Mating strategies and sexual systems

Since Darwin's early experiments on Lythrum and Primula, studies of heterostyly have contributed greatly to our understanding of genetics and morphological adaptation between flowers and their animal pollinators. These polymorphisms are maintained in populations by negative frequency-dependent selection and their functional significance in promoting cross-pollination is well understood. One of the advantages of heterostyly is the relatively direct linkage between floral morphology, inter-morph mating, and morph ratios, providing a visible signature of aggregate mating patterns in preceding generations. More recently, heterostyly and several related stylar polymorphisms have been investigated in a wider range of angiosperms, exposing considerable variation in the expression of hetero-styly and in the types of mating that can occur in populations. In Chapter 13, Spencer Barrett and Kathryn Hodgins contrast the symmetrical mating and equal morph ratios of typical heterostylous...

Reproductive assurance and selffertilization empirical approaches

Larson and Barrett 2000 Ashman et al. 2004). We now consider how the importance of RA in maintaining mixed mating can be tested, and then assess how RA can be isolated as a factor causing the transition from outcrossing to selfing in species with extensive mating-system variation. Wide variation in selfing versus outcrossing among closely related plant taxa and among populations within species has been used profitably for comparative analysis of mating-system evolution, as exemplified by Lloyd's (1965) landmark work on Leavenworthia. Variable taxa in Amsinckia, Arenaria, Clarkia, Eichhornia, Gilia, Lycopersicon, Mimulus, Phlox, Primula, and several other genera have provided insight into key issues, including the genetic basis and purging of inbreeding depression (e.g., Holtsford and Ellstrand 1990 Johnston and Schoen 1996 Busch 2005), the developmental and genetic bases of floral changes causing selfing (e.g., Holts-ford and Ellstrand 1992 Fenster and Barrett 1994 Fishman et al....

More experiments needed

The theoretical advances summarized in Table 10.1 strongly suggest that the intuitive appeal of reproductive assurance as a selective factor in the evolution of uniparental reproduction belies the challenges involved in testing it rigorously. Plenty of scope remains for new models to explore the genetic, physiological, demographic, and ecological feedbacks involved the evolution of the mating systems in environments with limited opportunities for out-cross pollination. However, the need for empirical tests of the assumptions and predictions of theory with biologically realistic experimental manipulations is even greater. Further empirical progress will first require estimates of the contributions of the various modes of selfing to the mating system and male and female fitness (Schoen and Lloyd 1992 Kalisz and Vogler 2003 Herlihy and Eckert 2004). In particular, the increased seed production afforded by autonomous selfing must be weighed against seed discounting, recognizing that the...

Pollinator responses to frequency definitions and importance

To a rare-morph advantage, resulting in stable polymorphism for the trait concerned (Clarke & O'Donald 1964). This behaviorally induced stability excited many behavioral ecologists, producing an explosion of studies on frequency-dependent choices of prey, mates, and hosts in natural populations reviewed by Allen 1988 O'Donald & Majerus 1988 Barrett 1988 see Clarke (1962) for shell-pattern polymorphisms in Cepea snails and Turner (1977) for wing-pattern mimicry in tropical butterfly species .

A special case selfpollination

Both theory and data support the idea that selfing species are good colonizers (Baker 1955 Lloyd 1979 Price and Jain 1981 Barrett 1996). Island populations tend to have reduced allozyme diversity relative to mainland populations (Glover and Barrett 1987 Inoue et al. 1996 Frankham 1997) and selfing phenotypes (small flowers, less herkogamy) often occur on islands or at species range margins (Stebbins 1957 Schoen 1982 Barrett et al. 1989 Inoue et al. 1996). In Clarkia xantiana, a small-flowered, selfing subspecies is found in marginal areas where specialist Clarkia bees are uncommon (Runions and Geber 2000 Fausto et al. 2001). Other studies suggest that pollinator rarity is important for selfing but have limited data on the pollinator community (Schoen and Brown 1991 Ramsey and Vaughton 1996), and few studies have done the relevant manipulative experiments (i.e., emasculation) to clearly demonstrate the link between pollinator scarcity and increased selfing ability. In three...

Harsh abiotic environment

Case 2000 Case and Barrett 2004a other traits, i.e., photosynthetic rates. Delph (2003) recently reviewed observational evidence for sexdifferential plasticity in several gynodioecious species. However, a few studies have also explored sex-differential plasticity by resource manipulation. Findings are somewhat mixed, possibly owing to genetic variability in the subject material (see above) or difficulties of maintaining appropriately divergent growth conditions. In an elegant in situ manipulation of Nemophila menziesii, Barr (2004) found that supplemental water increased seed production by hermaphrodites but not by females, with no sex-differential changes in plant size in the drier of two sites. In contrast, Dorken and Barrett (2004) found more variable flower production by females from dioecious populations of Sagittaria latifolia than by males in response to high nutrients. In other studies, the direction of sex-differential plasticity depended on the trait measured. For example,...

Harsh environments alter pollination pollen movement and mating system

The female outcrossing rate of hermaphrodites is a key parameter in sexual-system evolution, and studies indicate a range of mating systems, primarily involving a mixture of selfing and outcrossing (reviewed in Collin 2003). However, the factors causing mating-system variation or the genesis of mixed mating are poorly known (Goodwillie et al. 2005 Chapters 4 and 6). Several authors have suggested that harsh environments either support different pollinator faunas (Ganders 1978 Delph 1990a Weller et al. 1990) or alter plant phenotypes in ways that change pollen movement or the mode of selfing, thereby modifying the mating system (Case and Barrett 2004b Vaughton and Ramsey 2004 Chapter 7). I now review the limited existing data concerning these effects and then illustrate how resource-mediated changes in plant phenotype can alter the sufficiency of pollination, the mode of self-pollination, and the potential for pollen discounting, and thus ultimately the sexual system. Changes in plant...

Pollinators facilitators or inhibitors of sexualsystem evolution

Pollinators have been ascribed two important, but conflicting, roles in gender evolution. On one hand, reductions or shifts in faunal composition of pollinators may lead to insufficient or inferior pollination, respectively (see Harder and Barrett 1996), increasing autonomous or competing selfing of hermaphrodites and in turn facilitating the spread of females. On the other hand, if newly established females attract fewer pollinators, receive insufficient pollination, and thus suffer greater pollen limitation of their seed fertility, then they may not spread. No studies address the first scenario directly. Several studies have tested, but found limited evidence supporting, the second prediction (Shykoff et al. 2003), suggesting that pollinators are important in the initial invasion by females, but that pollen limitation does not impede female spread. This outcome could arise for two reasons. First, pollinators may disperse outcross pollen more efficiently to females than among...

Bumble bee behavior on artificial inflorescences

Although bumble bees may show frequency dependence on simple artificial flowers, they might not exert frequency-dependent selection in real populations. First, patterns of behavior might be affected by the organization of flowers into inflorescences encountering many flowers clustered together could affect a bee's perception of frequency. Second, even if visitation rates are well correlated with female function through seed set (Waser & Price 1981), they may be weakly coupled to other components of fitness such as outcrossing through male function (Stanton et al. 1986, 1989). In particular, if pollinators visit more flowers per inflorescence on one morph, more pollen will be transferred between flowers within inflorescences of that species (Klinkhamer & de Jong 1993 Harder et al., this volume). This will cause geitonogamous selfing in self-compatible species, and may block receipt of compatible pollen in self-incompatible species it will also reduce the amount of pollen...

Singleevent versus recurrent colonization

Continue to be linked following colonization by migration. This difference has important implications. Both single-event and recurrent colonization will act as a sieve that favours propagules capable of establishment following long-distance dispersal (Baker 1955 Pannell and Barrett 1998). Similarly, both processes are also likely to displace the genetic architecture of colonized populations away from evolutionary equilibria established at their source. However, this potential displacement may be more temporary following recurrent than single-event colonization, because only in the former instance can subsequent migration of genotypes not present among the original colonizers allow selection to restore a population quickly to its evolutionary equilibrium. Restoration of new evolutionary equilibria might be much more protracted in island populations, with colonized populations evolving trait combinations not found in their source.

Longdistance dispersal to oceanic islands

Islands have more self-compatibility amongst hermaphrodites and a higher proportion of dioecious species than those on continents (reviewed in Barrett 1996). The low frequency of self-incompatibility on islands is consistent with Baker's law, namely that colonization should select for uniparental reproduction, including self-fertilization, because it offers reproductive assurance in the absence of mates (Baker 1955, 1967). In contrast, the high relative incidence of dioecy on islands would seem to contradict Baker's law. 1995), they may be more likely to reach islands than non-dioecious species that are not dispersed by birds (Bawa 1980). Third, dioecious species, which tend to be pollinated by small generalist insects (Bawa and Opler 1975 Charlesworth 1993), may be pre-adapted to establish on islands, where generalist pollinators are also prevalent (reviewed in Barrett 1996). Fourth, because dioecious species tend to be long-lived perennials (Renner and Ricklefs 1995), or are...

Evolution of sexual systems in a metapopulation

Population from all other populations of the species. In this sense, it resembles long-distance colonization of oceanic islands, and it differs from colonization in a metapopulation, in which populations may be linked by migration. The evolution of sexual systems and other life-history traits in a metapopulation is particularly interesting, because it brings into focus the relative importance of three processes local evolution, which takes a population to a new equilibrium migration, which restores an old one and the stochastic ecological sieve imposed by colonization itself, which introduces a novel level of selection (Barrett and Pannell 1999 Ronce and Olivieri 2004 Pannell et al. 2005 Pannell and Dorken 2006). These interactions are well illustrated in their effects on the selection of uniparental reproduction, which confers reproductive assurance during colonization (Lloyd 1979 Pannell 1997a Pannell and Barrett 1998 see also Chapter 10). The evolution of self-fertilization in...

Conclusions the costs of mutualism

While mutualistic interactions have become accepted as comparable in importance to ecosystems as competition and predator-prey relationships, the view that mutualism represents cooperation between species has been challenged. Bronstein (2001) has stressed that mutualisms involve costs for each species, as well as benefits. Costs of mutualism are only now being tabulated, and there is little consistency in how data are gathered. Bronstein (2001) cites the following examples (i) 20 of the total carbon budget of forest trees may be consumed supporting mycorrhizae (Johnson et at. 1997) (ii) 3 of the energy budget of many plants is devoted to providing floral nectar for pollinators (Harder and Barrett 1992) (iii) extrafloral nectar costs about 1 of the energy budget of the plants involved (O'Dowd 1979, 1980). In the obligatory interaction between figs and their wasp pollinators, Bronstein (2001) estimated that 53 of ovaries of Ficus aurea are lost to the wasps, while yuccas (Yucca spp.)...

Evolution of dominant versus recessive traits in a metapopulation

First, genetic drift in small local populations or demes favours fixation of the morph determined by a recessive allele at the expense of the morph determined by a dominant allele (Barrett et al. 1989 see also Pannell and Barrett 2001). For example, consider an outcrossing gynodioecious population with nuclear sex determination, and suppose that the equilibrium frequency of females is x. If the female-determining allele is dominant, its equilibrium frequency is x 2, whereas if it is recessive, its equilibrium frequency is 1 (x 2), which exceeds x 2 for all x < 1. Being less common, the dominant allele is more susceptible to loss by genetic drift. Thus, more small populations in a polymorphic metapopulation should be fixed for the recessive allele than for the dominant allele. This local fixation bias will contribute to a global deficit of the dominant allele and its associated morph (Barrett et al. 1989 Pannell et al. 2005). Interactions between negative frequency-dependent...

Modes of selfing and the evolution of geitonogamy

Pannell and Barrett (1998) analysed the relative general benefits of selfing versus outcrossing in a metapopulation, but they did not consider mating between selfers and outcrossers, nor the implication of specific modes of selfing, so several interesting questions remain. First, under what conditions can a genetic variant invade and spread in a self-compatible population comprising individuals with floral traits that limit the possibility of geitonogamy Second, having invaded a population, should such a variant then spread to fixation, completely replacing the outcrosser, or be maintained at an intermediate frequency in a polymorphic population This second question impinges on the more general question concerning the maintenance of selfing-outcrossing polymorphisms, which models have shown to be difficult (Pannell and Barrett 2001). Third, when a geitonogamy-outcrossing polymorphism is maintained in a metapopulation, to what extent does the dominance or recessivity of the variant for...

The evolution and functional basis of floral and sexualsystem diversity

Floral morphology and sexual-system diversity are closely associated in Narcissus, implying a functional basis to their correlated evolution. Narcissus flowers are insect pollinated and comprise three basic components the floral tube, free tepals, and the corona. Floral diversity within the genus evolved largely through changes in the relative sizes of these floral structures. Barrett and Harder (2005) distinguished several distinct floral designs in Narcissus, two of which are common. In the ''daffodil'' design (Plate 3a) the floral tube is short and the corona is large and cylindrical or trumpetlike, allowing bees to enter the flower completely while foraging for nectar and or pollen. This morphology characterizes section Pseudonarcissus (trumpet daffodils) and all species possess stylar monomorphism. In contrast, the ''paperwhite'' design (Plate 3c) is found in diverse sections (e.g., Apodanthi, Jonquillae, Narcissus, Tazettae) and has a short flaring corona and a relatively long,...

Mating in monomorphic populations

Narcissus longispathus exhibits mixed mating, producing significant numbers of both outcrossed and selfed seeds (Barrett et al. 2004a tm 0.54 - 0.77 N 6 populations). Marker-based estimates of inbreeding depression (see Ritland 1990) indicate that few selfed seeds survive to maturity, a pattern also reported in N. triandrus (Hodgins and Barrett 2006a), so that selfing provides little reproductive assurance. Estimates of the proportion of outcrossed seed and the inbreeding coefficient for samples from the same population obtained 13 years apart yielded very similar values, indicating remarkable stability in mixed mating and inbreeding (Medrano et al. 2005). The strong selection against selfed offspring in N. longispathus raises the intriguing question of why selection has not produced floral mechanisms that reduce this significant waste of zygotes.

Mating in dimorphic populations

Stigma-height dimorphism is the most common stylar polymorphism in Narcissus, even though this condition is rare among angiosperms (Barrett et al. 2000). This polymorphism occurs in at least a dozen Narcissus species, distributed among three sections (Apodanthi, Jonquillae, Tazettae). Populations with stigma-height dimorphism contain two floral morphs that differ in style length (hereafter L- and S-morphs) however, in both morphs the two anther levels within a flower occupy similar positions at the top of the floral tube. Therefore, unlike distyly, reciprocity between the stigma and anther heights is weak. Stigmas of the L-morph correspond in height to the upper-level anthers of both morphs, whereas stigmas of the S-morph are positioned below the lower-level anthers (Fig. 13.2b). Consequently, the S-morph exhibits large stigma-anther separation, whereas herkoga-my is either weakly developed or absent in the L-morph. Weak sex-organ reciprocity has important consequences for pollen...

Socioeconomic Feature

There is a notable variation in the number of dogs between villages. Luapa has the most (+300), with one individual owning as many as 15 dogs, and other villages having < 100. Dogs are essential in the hunt. During data analysis, we used this as an indicator of who is doing the most hunting. Hunting is performed either alone or in the community group with (in rank order of preference) 1) black-fronted duiker (unanimously the preferred meat) 2) blue duiker 3) bay duiker 4) red river hog 5) yellow-backed duiker and 6) generic monkeys, as the species generally targeted. Iyaelima hunting technology is limited to dogs, spears, and bows and arrows for individual hunts, and nets are added during the village hunts. In the mid-1990s, the government confiscated all firearms from the civilian population, leaving only traditional technology for hunting. Village hunts are called once every 1-2 weeks during the dry season. Hunting for domestic consumption is the principal occupation of the men...

Evolution and maintenance of stigmaheight dimorphism

Theoretical and experimental evidence from Narcissus indicates that stigma-height dimorphism increases the proficiency of cross-pollination and limits self-interference (Lloyd and Webb 1992b Barrett et al. 1996 Thompson et al. 2003 Cesaro et al. 2004 Cesaro and Thompson 2004). The establishment of stylar dimorphism requires the invasion of a monomorphic population with approach herkogamy by a short-styled variant. In Narcissus, short styles are governed by a dominant allele at the style-length locus (L-morph ss S-morph Ss or SS Dulberger 1967). Therefore an advantageous short-styled variant should spread easily in populations, because all individuals with the dominant allele express the novel phenotype (Haldane 1927). This pattern of inheritance also occurs in most distylous species, indicating the important role of dominance in the invasion dynamics and inheritance of stylar polymorphisms (Lloyd and Webb 1992a). Theoretical models indicate that the maintenance of stigma-height...

Asymmetrical mating and biased morph ratios

Interactions between pollinators and flower morphology are probably the main cause of the variation in morph ratios among N. assoanus populations. Variation in selfing rates caused by differences in herkogamy or partial self-incompatibility do not account for the predominance of the L-morph in populations (Baker et al. 2000b). Populations are highly outcrossing (Table 13.1), so biased morph ratios probably result from differences between morphs in patterns of inter- and intra-morph mating. Specifically, the S-morph should be less proficient at intra-morph mating than the L-morph because of its well-developed herkogamy. In contrast, stamen positions in the L-morph have presumably been optimized for efficient cross-pollination in ancestral populations (Fig 13.2a), and in monomorphic populations of the L-morph that occur commonly in several species with stigma-height dimorphism (reviewed in Arroyo et al. 2002). Theoretical models of asymmetrical pollen transfer and mating confirm that...

Evolution of morph ratios

Geographical surveys of morph frequencies can provide insights into how polymorphisms are maintained in the face of strong environmental gradients. Our surveys of N. triandrus have revealed patterns unlike those reported for other tristylous species (Barrett et al. 1997, 2004b), including (1) a predominance of the L-morph in populations (2) a negative relation between the frequencies of the L- and M-morphs and (3) dimorphic populations missing the M-morph. Significantly, although populations of both N. tri-andrus varieties are usually L-morph biased, tri-morphism is only a stable feature of var. cernuus populations. In N. triandrus var. triandrus the M-morph becomes relatively less common in the northwest of the Iberian Peninsula (fig. 3a in Barrett et al. 2004b), with several geographically separated transitions between trimorphic and dimorphic populations (Plate 4). Our work attempts to elucidate the mechanisms that account for these patterns. Figure 13.4 The influence of floral...

Variation and evolution of sexual organs

Sex-organ position in N. triandrus varies extensively compared with most other tristylous species (fig. 12 in Eckert and Barrett 1994). This variation is manifested both within and among populations and suggests spatially variable selection. Bateman (1968 p. 645) proposed that the high variation in style length in N. triandrus represents ''an early stage in speciation through divergent adaptation to different pollinators'' an improbable claim given the maintenance of stylar polymorphism throughout the species' range. We consider it more likely that geographical variation results, in part, from changes in the types of pollinators that service populations. For example, flower size increases along the southeast-northwest gradient of M-morph frequencies, with accompanying differences in allometric relations of sex-organ position (Barrett et al. 2004b). Although the proximate ecological mechanism responsible for the flower-size cline appears to be rainfall related changes in overall plant...

Selected key references

Barrett SCH, Harder LD, and Worley AC (1996). The comparative biology of pollination and mating in flowering plants. Philosophical Transactions of the Royal Society of London, Series B, 351, 1271-80. Dodd ME, Silvertown J, and Chase MW (1999). Phylo-genetic analysis of trait evolution and species diversity among angiosperm families. Evolution, 53, 732-44.

Villagebased Data Collection

We complimented field data on hunting indicators recorded on recces and transects with information on hunters and hunting practices gathered from interviews and direct observations by trained observers in villages located outside the park in the vicinity of the Phase II Lokofa Block and an immediately adjoining area covering about 2000 km2, the Lokolo Block. The data includes village censuses, inventories of hunting equipment (snares and shot guns) and counts of hunting dogs. We

Ecological genetics of quantitative traits

Three approaches are used to estimate herit-abilities, genetic correlations, and their unstan-dardized counterparts, genetic variances and covariances (the G matrix). The most common method involves the mating designs that plant and animal breeders have used for decades, such as offspring-parent regression, sibling analysis, and diallel mating crosses (Falconer and Mackay 1996 Conner and Hartl 2004). These techniques use controlled crosses to create sets of individuals of known genetic relationship, and then regression or analysis of variance to estimate genetic variances and covariances. For example, Campbell (1996) used both offspring-father regression and half-sibling analysis to demonstrate significant herit-ability for corolla length, width, and the positions of anthers and stigma of scarlet gilia, as well as genetic correlations among most traits. Many studies have used mating designs to estimate genetic variances and covariances for floral traits (e.g., Shore and Barrett 1990...

Behavioral responses of pollinators to variation in floral display size and their influences on the evolution of floral

Numerous studies have reported that variation in floral display size produces marked alterations in pollinator behavior. Especially, two types of pollinator response to increased floral display size have been recognized from the perspective of their influences on pollen dispersal. First, larger floral displays attract more pollinators per unit of time (Fig 14.1A reviewed by Ohashi & Yahara 1998). This will promote cross-pollination in terms of increased pollen receipt, removal, or potential mate diversity (Harder & Barrett 1996). Second, the number of flowers that individual pollinators probe per plant also increases with floral display size (Fig. 14.1B also reviewed by Ohashi & Yahara 1998). This will increase self-pollination among flowers on the same plant (geitonogamy Richards 1986 de Jong et al. 1993). Thus, variation in floral display size may lead to a substantial difference in pollen dispersal and, in turn, plant fitness.

Human Occupation and Hunting in the Salonga National Park

Hunters operating in the Salonga National Park use active pursuit with bow-and-arrow or 12-guage shotguns, and snares and traps. The primary targeted species are medium-sized ungulates (duikers and pigs) and monkeys. Hunters also target larger rodents, birds, reptiles and small carnivores using pitfalls, snare lines along barriers and other specialized methods however, these smaller species comprise only a minor portion of the bushmeat consumed and sold. Differences in hunting methods between communities are mainly in the relative importance of pursuit versus snares, in the prevalence of the use of firearms, and the degree to which dogs are used.

Natural selection on floral traits

The importance of male fitness for floral evolution has been recognized for more than 25 years (Willson and Price 1977), based on Bate-man's principle (Bateman 1948), which predicts stronger selection on floral traits through differences in male fitness than through differences in female fitness. This prediction applies when the availability of resources other than pollen, such as light, water, or soil nutrients, limit female fertility, whereas male fitness depends on success in pollen export and ovule fertilization. Stanton et al.'s (1986) analysis of selection on flower colour in wild radish, discussed above, supported this prediction. How commonly Bateman's principle applies to plants has been subject to debate, as it depends largely on how commonly female fitness is pollen limited (Wilson et al. 1994 Larson and Barrett 2000 Ashman et al. 2004 Chapter 4). However, this debate does not diminish the relevance of male fitness in floral adaptation, because half of all...

Faunal Occurrence and Hunting Indices

Firearms We recorded indicators of hunting, including 26 direct encounters with hunters, in 165 (51 ) of 325, 10 x 10 km Phase I quadrats (Fig. 12.2). Snares and hunting camps were the most frequently observed indicators. We noted spent shot gun cartridges and specialized traps, such as pits falls, on just a few occasions, and rarely heard gunshots. The infrequency of spent ammunition can be accounted for by the fact that most hunters retrieve and reload spent cartridges. We recorded fishing

Village and Hunter Surveys

Table 12.3 is a summary profile of the surveyed villages. Although the Lokofa and Lokolo communities have approximately the same number of inhabitants, the villages bordering the Lokolo Block have more hunters than the villages bordering the Lokofa Block. Both Lokofa and Lokolo villages had comparable equipment indices (snares per hunter and shotguns per hunter) with dogs used frequently in both areas. Lokolo villages had higher involvement in the commercial meat trade than Lokofa Block villages (7 vs. 4) and a greater presence of mobile professional hunters (12 vs. 3). All of the 20 hunters encountered by survey teams within the park in the Lokofa Block during Phase II inventories were based in just two villages, and almost all were Iyeke pygmies. In the Lokofa villages, only one of the three professional hunters we interviewed had his own camp in the forest at the time of the survey. Two had rented their cable snares and shot guns to local hunters in exchange for a share of the...

Threats to Bonobos in the Salonga National Park

1) High hunting indices Intensive hunting is a threat to bonobos even when they are not targeted, since the non-selective hunting methods widely used in the park (cable snares) are likely to catch, maim or kill bonobos, as has been documented with chimpanzees (Hashimoto 1999, Reynolds et al. 1996). Bonobos are also likely to be killed opportunistically by hunters with firearms when they are encountered. Areas with high hunting levels are likely to include a higher proportion of mobile professional hunters who may be more inclined to seek and kill bonobos.

Californias Oak Woodlands

Since European settlement of California, oak woodlands have been managed primarily for livestock production. These areas have taken on a new importance since the recognition that they have the richest species abundance of any habitat in the state, including more than 300 vertebrate species, 5,000 invertebrate species, and 2,000 plant species (Verner 1980, Barrett 1980, Garrison 1996). Oak woodlands also enhance the water quantity and quality, outdoor recreation, and aesthetic effect of the region. Over 80 of California's oak woodlands are in private ownership (Greenwood et al. 1993).

Game Preservation in Britain 18701914

European farmers and hunters have destroyed predators for centuries (Reynolds & Tapper 1996 McDonald & Murphy 2000), but the most efficient and systematic form of this deadly campaign evolved on privately owned sporting estates, especially in Britain after the 1860s. Game birds were required in large numbers, especially for driven shoots using the modern range of sporting firearms. Under British law, all forms of wildlife were then the legal possession of the landowner, who was usually disinclined to share them with natural predators or with people other than invited guests. Gamekeepers were supplied with guns, poisons, and the newly developed steel kill traps. They proudly displayed their catches on gibbets (rows of carcasses hung up by the necks) (Yalden 1999) as evidence of their hard work (Figure 12.2), and some even turned this deadly trade into an art form.

Reticulate evolution and fruit crops citrus

The origin of the genus, Citrus, is hypothesized to have occurred in the subtropical and tropical zones of Southeast Asia, followed by dispersal to other continents (see Nicolosi et al. 2000 for references). However, the evolutionary relationships among the cultivated species have been difficult to discern, likely due to extensive hybrid lineage formation and introgression (Moore 2001). In this regard, Barrett and Rhodes (1976) argued for the recognition of only three true biological species, those being C. grandis (pummelo), C. medica (citron), and C. reticulata (mandarin). The remaining Citrus domesticated species were recognized as having a hybrid derivation (Barrett and Rhodes 1976 Nicolosi et al. 2000 Moore 2001 de Moraes et al. 2007). Figure 7.8 The reticulate evolutionary history of grapefruit, lime, lemon, pummelo, citron, mandarin, and sour and sweet oranges (C. paradisi, C. aurantifolia, C. limon, C. grandis, C. medica, C. reticulata, C. aurantium, and C. sinensis,...

Evolutionary implications

Moreover, the model predicts that pollinators would show a weaker preference for visiting large floral displays over small ones at lower plant density. Such an effect could aggravate the relative disadvantage of larger displays growing at low densities it would reduce xenogamy and increase geitonogamy. To clarify these influences, we describe a model by incorporating pollinators' optimal behavior into the model of pollen transfer. We independently developed this model, but very similar theoretical ideas were developed by Iwasa et al. (1995), who tried to explain the small number of flowers probed by a pollinator per plant as a plant's strategy to maximize pollen dispersal. We assume that (1) pollen on a pollinator constitutes a single, homogeneous pool (2) a pollinator deposits and picks up pollen in equal amounts at each flower (pollination saturation de Jong et al. 1993) and (3) this amount is a constant fraction of the amount of pollen held on a pollinator's body....

Cognitive Landscape Versus Geographical Landscape

According to the approach that we intend to utilize, the landscape appears at the same time as a geographical entity, an aesthetic surface (Barrett et al. 2009), or a mental representation (Gould and White 1974, Lynch 1976, Gibson 1979, Kaplan and Kaplan 1989, Bourassa 1991, Appleton 1996, Ingold 2000).

The Luo Scientific Reserve

The goal of the Luo Reserve is to maintain the co-existence of bonobos and human inhabitants. Thus, the regulation of the reserve was designed to permit the traditional lifestyles of the villagers in Wamba. The following activities are prohibited to protect bonobos in the reserve hunting of primates, using guns, wire snares or poison arrows, and clearing primary forest. Other activities such as collecting plants, traditional hunting, and cultivation of secondary forest are allowed in the reserve. The establishment of the reserve served to educate the local people and government officers about the illegal killing of bonobos. Nevertheless, the villagers disliked the establishment of the reserve because they disapprove any restriction of their activities. They also complained that the compensation money to regulation of

Partial List Of Suppliers

Centrifugation Clinton Centrifuge Inc. ALFA Laval Inc. Tetra Recovery Systems Dorr-Oliver Inc. Bird Environmental Systems Western States Machine Fletcher Astro Metallurgical Barrett Centrifugals Donaldson Industrial Group GCI Centrifuges General Production Services Inc. IT Corp. Ingersoll Rand Environmental Master Chemical Corp. System Equipment Sartorius Balance Div., Brinkman Sharples Stokes Div., Pennwalt Tekmar Co. Thomas Scientific

Reproductive assurance and selffertilization theoretical context

Pannell and Barrett 2001 (2) temporal variability in pollination environments (3) physiological and demographic costs associated with seed discounting and (4) metapopulation dynamics. Table 10.1 summarizes the relevant theory Goodwillie et al. (2005) provided a more detailed discussion. Taken together, recent theory reveals that the role of RA in mating-system evolution might be much more complicated than previously thought. For instance, spatio-temporal variation in pollination environments enhances the fitness benefits of autonomous selfing, because RA increases geometric mean fitness (Schoen and Brown 1991 Morgan and Wilson 2005 Chapter 2). However, the potential cost of seed discounting extends well beyond the simple usurpation of ovules by self-fertilization. Because developing selfed seeds consume maternal resources, seed discounting can involve costly trade-offs between offspring quantity and quality, as well as reduced survival and future reproduction (Lloyd 1979 Morgan et al....

Flowers and pollen dispersal by individual pollinators

Theoretical features of pollen dispersal by a single pollinator from (a) a single flower and (b) a 50-flowered plant (see Harder & Barrett 1996). Panel (a) considers the pollination fates of pollen removed from the first of five flowers (the donor flower) visited by a pollinator on a focal plant (di rp i - p i-i, where d is the proportion of donor pollen received by recipient flower i, r is the proportion of available pollen removed from each flower, and p is the proportion of pollen carried by the pollinator that is deposited on the stigma of each flower). Panel (b) illustrates how pollen export from a donor plant (E) to other plants varies with the proportion of flowers that a pollinator visits per inflorescence (E r i - 1 - p vn p, where v is the proportion of the n open flowers visited by the pollinator). For both panels, r 0.2, p 0.1, and n 50 flowers. Fig. 15.1. Theoretical features of pollen dispersal by a single pollinator from (a) a single flower and (b) a...

Brief History of Landscape Ecology

Finally, spatial ecology focuses on a plethora of processes and patterns that are associated with space. Special emphasis is given to the study of animal behavior and to the relationship between habitat structure and organism function. An experimental approach using microcosms is of growing importance in the validation of spatially explicit models that apply statistical tools and fractal mathematics to plants and animals (e.g. Barrett and Peles 1999).

Vacuumfreeze Vapor Compression

Figure 8.6.7 shows the Zarchin-Colt process in which water is the refrigerant. Seawater, after prechilling in a heat exchanger to a temperature approaching the freezing point of brine, enters the freezer. Evaporation is induced by the suction of the compressor, which absorbs heat from the remaining brine. Ice crystals are formed, growing to about 0.5 mm. The ice-brine slurry is pumped to the ice decanter where ice crystals float to the top. There they are washed with a portion of the product water made. This washwa-ter moves downward and carries away salt. A rotating scraper trims the ice layer at the top and sends the washed crystals to the freezer, where they come into contact with the compressed water vapors. The water vapor condenses on the ice crystals suspended on a rotating perforated tray and melts them. (The ammonia refrigeration system shown in Figure 8.6.7 removes heat gain through insulation.) This melted ice is the desired fresh-water product. The cold fresh water and...

Ungulate Hunting and Pastoralism

The bison were nearly destroyed in a period of just fifty years. During the nineteenth century the expanding Euroamerican fur trade grew increasingly dependent on Indian hunters providing food and hides for the influx of settlers. The introduction of guns, diseases, and new markets for leather products in eastern North America upset the ecological balance traditionally maintained by native peoples and quickly led to the demise of the bison or American buffalo in the West (ibid., pp. 35-36). By the end of the nineteenth century, the great bison herds of the Plains had diminished to fewer than 1,000 animals. The horse is indigenous to North America, but it had long been extinct on the continent when it was reintroduced by the Spanish conquest of Mexico in 1519. West of the Great Lakes, the Indians upon whom the fur traders would come to depend began hunting bison on horseback. Horses were used to advantage in war, as well as in hunting and for transportation, communication, and trade....

Controlling poaching and the illegal trade in ivory

The manner in which elephants are poached varies considerably from one region to another. Uganda's elephants were indiscriminately slaughtered by soldiers during the internecine strife of the 1970s. In southern India, elephants have been poached opportunistically by small groups of villagers armed with crude firearms such as muzzle-loading guns, as well as by larger, better organized gangs armed with more advanced weapons. Elephants in remote areas of Cambodia's Cardamom Mountains are killed by traditional hunters operating singly or in very small groups. Elephants are still hunted across Indochina by local people using old-fashioned weapons such as poisoned arrows. Law enforcement capabilities also vary widely across the range states. Kenya has a professional wildlife service to manage and protect elephants. South Africa's national parks service holds a tight rein on their elephant populations. On the

History of the ivory trade with special reference to Africa

A sharp rise in the price of ivory during 1856-1857 saw Arab traders rushing into the region. Soon, a very large number of firearms entered East Africa, further stimulating the hunt for ivory. Zanzibar exported 222 tonnes in 1889 and continued this with an annual average of 180 tonnes until the end of the century. The 40,990 tusks exported during 1893-1894 weighed 351 tonnes. Thus, at least 10,000 elephants were contributing to the trade from the region each year, presumably most of them having been hunted. Apart In 1900, two travelers, Grogan and Sharpe, wrote that, In the greater part of Africa the elephant is now a thing of the past and the rate at which they have disappeared is appalling. Ten years ago elephants swarmed in places like British Central Africa, where now you will not find one (quoted in Spinage 1994, p. 253). Although not entirely true, this was a fair statement of the elephant's status over much of Africa, particularly the savannas, at the entrance to the twentieth...

The Interior West

According to Clary and Tiedemann, while there is little information on which to project long-term changes in the density or distribution of Gambel oak, there is some evidence that Gambel oak clones (expanding as rhizomes) may have increased in number and size since the turn of this century. Gambel oak is very important as a source of food and winter cover for wildlife. In recent years, suburban home development has been encroaching into some of these areas (Barrett 1995). In some areas, fire, herbicides, and mechanical removal have been used to offset the dominance of Gambel oak by expanding forage and accessibility for livestock and large game. Because Gambel oak is highly valued for fuelwood, fuelwood sales are combined with oak stand management in some areas. Management aimed specifically at Gambel oak is not common.

General Conclusions

In general, our study warns against generalizations derived from studies on a single bonobo group. For instance, the typical bonobo-pattern of female bondedness (Parish 1996) is confirmed by the data on coalitionary support in several groups, but not by the grooming patterns. Further, the dominance related bonding patterns described in the Planckendael group of 1999 (Vervaecke et al. 2000b) no longer persist in the changed group. In some groups, dominant individuals received more grooming or support than subordinates, and in other groups support or grooming was reciprocal (Stevens et al. 2005). However, this variation could be related to variation in dominance steepness, as predicted by biological market theories, wherein one expects reciprocal exchange in groups with a shallow dominance hierarchy, and up-the-hierarchy grooming and interchange of commodities in groups with a more steep dominance gradient (Barrett et al. 1999). Grooming was indeed more reciprocal in groups with a...

WouldBe Worlds

For the past 3 years, a team of researchers at the Los Alamos National Laboratory headed by Chris Barrett has built an electronic counterpart of the city of Albuquerque, New Mexico, inside their computers. The purpose of this world, which is called TRANSIMS, is to provide a testbed for studying the flow of road traffic in an urban area of nearly half a million people. In contrast to Tierra, TRANSIMS is explicitly designed to mirror the real world of Albuquerque as faithfully as possible, or at least to mirror those aspects of the city that are relevant for road-traffic flow. Thus, the simulation contains the entire road traffic network from freeways to back alleys, together with information about where people live and work, as well as demographic information about incomes, children, type of cars, and so forth. So here we have a would-be world whose goal is to indeed duplicate as closely as possible a specific real-world situation.

Figure 428

Species of the genus Ranunculus (buttercup) inhabit a range of moisture conditions from upland to submergence. Those species that inhabit either wet terrestrial or dry terrestrial habitats with stable water levels are inflexible in leaf shape. However, R. flammula, which inhabits the fringe of water bodies where water levels fluctuate, is flexible in leaf shape and displays the greatest level of heterophylly within the genus (Figure 4.30 Cook and Johnson 1968 Barrett et al. 1993).

Herbivory

Intriguingly, the most dramatic effects of invertebrate grazing on living aquatic macrophytes involve herbivores derived mainly from terrestrial insect lineages. These include chrysomelid and curculionid beetles, aquatic and semiaquatic lepidopterans, and specialized dipterans (Newman 1991). At a site in the Ogeechee River, Georgia, infested with the water lily leaf beetle Pyrrhalta nymphaeae (Chrysomelidae), leaves of the water lily Nuphur luteum lasted only 17 days compared to more than 6 weeks at another site where the beetle was absent (Wallace and O'Hop 1985). Some macrophytes, including the water hyacinth Eichornia crassipes and the kariba weed Salvinia molesta, can become so abundant that they present serious weed control problems worldwide, particularly in the subtrop-ics and tropics. A Brazilian beetle that feeds on kariba weed is one potential agent of biological control (Barrett 1989).

The system

The following studies focus primarily on Phyllonorycter salicifoliella (Chambers) (Lepidoptera Gracillariidae), an abundant leaf-mining moth on willows at our study site. Eggs are laid on lower leaf surfaces, and mines are formed on the underside of leaves, as the larva passes through sap-feeding and tissue-feeding stages. Causes of larval mortality can often be determined for this species (Pottinger and LeRoux, 1971 Auerbach and Alberts, 1992 Faeth, 1992 Fritz, 1995). One major source of mortality for Phyllonorycter is parasitoid attack. Phyllonorycter is parasitized by the internal larval parasitoid Pholetesor salicifolielliae (Mason) (Hymenoptera Braconidae) (J. Whitfield, 1990, personal communication). The white silken cocoons of this species, which are strung on silk threads in the mines, identify Pholetesor. External larval parasitoids include several genera of Eulophidae (Hymenoptera) (Sympiesis, Pediobius, Achrysocharoides, Chrysocharis) (M. Schauff and E. Grissell, 1990,...

Stlv Stlv

Three main factors can cause patterns of infection to differ between males and females (Zuk and McKean 1996 Combes 2001). First, body size dimorphism should require that males consume more resources, thus exposing them to more infectious stages of parasites. Their larger nutritional requirements could also make males more susceptible to infections (Barrett and Henzi 1998). Second, males and females are likely to differ in their exposure to directly transmitted parasites due to sex differences in social relationships, variation in access to mates, and differences in diet or habitat (Meade 1984 Nunn and Altizer 2004). Finally, sex differences in hormones could account for

Acknowledgements

Barrett, and two anonymous reviewers for useful suggestions and encouragement while writing this chapter and R. Aguilar for allowing us the use of unpublished material. Research leading to this work was supported by a postdoctoral fellowship to DPV at the National Center for Ecological Analysis and Synthesis (funded by the University of California, Santa Barbara, and the National Science Foundation, USA). MAA and DPA are researchers with the National Research Council of Argentina (CONICET).

Conclusions

Paniculata (Barrett et al. 1989), or does Haldane's sieve also need to be invoked (Pannell et al. 2005) Single-event and recurrent colonization affect sexual-system evolution in both similar and different ways. Essentially, whether their effects are comparable or different depends largely on the extent to which colonization isolates the colonizing lineage from the influence of subsequent migrants. The most interesting, but also the most complex, situations are likely to be those in which migrants play a role that is neither negligible nor overwhelming. Such cases should exhibit evidence for both the effect of the selective sieve imposed by colonization and the subsequent evolution of lineages in (partial) isolation from one another. The populations of dynamic metapopulations within a region are likely to show the former, but perhaps not the latter. In contrast, related species evolving in allopatry may show independent evolution, but signatures of the selective sieve will quickly...

Hifilqkjfk

Where si is the number of seeds produced by morph i, qj is the proportion of pollen exported from morph i to morph j, and fi represents the frequency of the ith morph. We assume that individuals of all morphs export equivalent amounts of pollen and do not differ in their maternal selfing rates, which has been confirmed for N. triandrus (Hodgins and Barrett 2006a). The first term on the right side, s 2, represents a morph's contribution of genes as a maternal parent and the remaining terms represent a morph's paternal contribution realized through pollen competition in the pistils of the L-, M- and S-morphs, respectively. The matrix of pollen-transfer proficiencies is presented in Barrett et al. (2004b). highest proportional seed set and least common in populations where its female fertility was significantly lower than the other two morphs (Hod-gins and Barrett 2006b). This result contrasts with expectations for typical tristylous species. Negative

Discussion

Sexual polymorphisms in Narcissus were first reported over a century ago (Wolley-Dod 1886 Henriques 1887) and later became a source of controversy (Fernandes 1935, 1965 Bateman 1952, 1968). However, not until David Lloyd and colleagues (Lloyd et al. 1990 Barrett et al. 1996) alerted floral biologists to the rich diversity of sexual systems in Narcissus did modern experimental investigations begin in earnest. Subsequent work during the past decade on the floral biology, pollination and mating systems of Narcissus species have been facilitated by collaboration among several research groups and has resulted in the publication of 20 journal articles (see References) and several doctoral dissertations. Most cases of asymmetrical mating in hetero-stylous populations are associated with morph-spe-cific differences in selfing rate caused by the weakening or loss of heteromorphic incompatibility. In some cases, asymmetrical mating promotes the evolutionary breakdown of heterostyly and its...

Eucitortreated

Figure 10.5 Plant cell cultures have proven to be very useful for studying plant-pathogen interactions and isoprenoid metabolism. Tobacco cell cultures respond rapidly to the addition of fungal elicitors (0.5 pg cellulase ml of culture) by browning (A) (analogous to a hypersensitive response) and the production of phytoalexins (B). Media was collected from elicited cell cultures at the indicated times, partitioned against an organic solvent, and concentrated aliquots run on a silica TLC plate. The plates were then sprayed with a suspension of Cladosporium cucumerinum spores and incubated in a humid environment for 5 days before viewing (B). The compound released from the elicitor-treated tobacco cells that inhibits spore germination is capsidiol, a sesquiterpene.

Figure

Its flowers are insect-pollinated and self-compatible. Pollination appears to be more successful in tropical areas where insect pollinators are more numerous. Flowering begins 10 to 15 weeks after germination and one inflorescence with 20 flowers produces up to 3000 seeds. Up to four inflorescences can be produced by a single rosette in a 21-day period. In the tropics and subtropics, E. crassipes flowers for 5 to 9 months. The seeds are released in capsules of 40 to 300 seeds each that either sink or accumulate in the floating mat. Germination of seeds in the sediments is prevented if the sediments are shaded or light levels and temperatures are low. Most new individuals arise through asexual reproduction when daughter rosettes formed on nodes along stolons detach from the parent plant (Barrett 1980a, b Haynes 1988 Harley et al. 1996).

Pollinator economics

1992 Rasheed & Harder 1997& ) whether to move to a neighboring, or more distant plant (Cibula & Zimmerman 1984) whether to start feeding on a different plant species (Zimmerman 1981) and when to end a foraging bout and either return to the nest or transfer to another behavior (Schmid-Hempel et al. 1985). Three features of the involvement of a benefit-cost ratio in these decisions warrant notice. First, as will become apparent below, all of these behaviors influence the pattern of pollen dispersal, so that foraging currency defines the linkage between many floral characteristics and pollination success. Second, the consequences of a floral characteristic, such as nectar volume or concentration, for pollinator behavior depends on its influence on the relevant foraging currency, rather than its effects on benefits or costs alone (e.g., Harder & Real 1987). Finally, because the value of a particular behavior to a pollinator depends on the average currency in the environment,...

Inflorescences

The presence of multiple flowers permits pollen transport between a plant's own flowers (reviewed by Harder & Barrett 1996 Snow et al. 1996 also see Brunet & Eckert 1998 Rademaker & de Jong 1998). In general, geitonogamy increases as a pollinator visits more flowers on a plant. For example, consider the destinations of pollen removed from the first of five flowers visited by a pollinator on a plant (Fig. 15.1a). Geitonogamous pollen transfer from this flower occurs during the pollinator's next four flower visits. If, instead, the pollinator visited eight additional flowers on the same plant, geitonogamy would claim a larger fraction of the total pollen dispersed from the donor flower and the plant as a whole. Because pollinators tend to visit more flowers on larger inflorescences (reviewed by Ohashi & Yahara, this volume), geitonogamy generally increases with display size (reviewed by Harder & Barrett 1996 Snow et al. 1996). In addition to increasing the number of...

Mineral Nutrition

Calcium deficiency is rarely observed in conifers, even if its uptake is limited by soil acidification. In hydroponics, the visual symptoms of calcium deficiency include browning of twig tips, followed by their senescence (BAULE and Fricker 1973). In spruce seedlings, INGESTAD (1959) observed yellowing of young needles, whereas all needles had yellow or brown tips and postponed development of apical buds. Root growth was also poor they were short and densely branched. Calcium deficiency reduces plant height, but the response of Norway spruce is less than that of other coniferous trees. The uptake of individual elements and their concentration in plants depends mainly on their concentration in the substrate, and generally increases with increasing concentration in the culture medium. Nitrogen is taken up as ammo Interactions among individual nutrients can be observed. A higher nitrogen supply reduces the concentrations of phosphorus and potassium in needles of 3-year-old spruce...