For discussions over the years and comments on the manuscript I thank Diane Campbell, Lars Chittka, Reuven Dukas, Carlos Herrera, Scott Hodges, Jeff Ollerton, Mary Price, Graham Pyke, James Thomson, Bob Vickery, Paul Wilson, and Paul Wolf. Many of our studies ofIpomopsis were supported by the United States National Science Foundation.


Alarcon R & Campbell DR (2000) Absence of conspecific pollen advantage in the dynamics of an Ipomopsis (Polemoniaceae) hybrid zone. Am J Bot 87:819-824 Arnold ML (1997) Natural hybridization and evolution. Oxford University Press, New York

Arnold ML, Hamrick JL & Bennett BD (1993) Interspecific pollen competition and reproductive isolation in Iris. J Hered 84:13-16 Baker HG (1963) Evolutionary mechanisms in pollination biology. Science 139:877-883 Bradshaw HDJ, Wilbert SM, Otto KG & Schemske DW (1995) Genetic mapping of floral traits associated with reproductive isolation in monkeyflowers (Mimulus). Nature 376:762-765

Campbell DR & Waser NM (2001) Genotype by environment interaction and the fitness of plant hybrids in the wild. Evolution in press Campbell DR, Waser NM & Meléndez-Ackerman EJ (1997) Analyzing pollinator-

mediated selection in a plant hybrid zone: hummingbird visitation patterns on three spatial scales. Am Nat 149:295-315 Campbell DR, Waser NM & Wolf PG (1998) Pollen transfer by natural hybrids and parental species in an Ipomopsis hybrid zone. Evolution 52:1602-1611 Chittka L, Thomson JD & Waser NM (1999) Flower constancy, insect psychology, and plant evolution. Naturwiss 86:361-377 Cotton PA (1998) Coevolution in an Amazonian hummingbird-plant community. Ibis 140:639-646

Coyne JA & Orr HA (1997) "Patterns of speciation in Drosophila" revisited. Evolution


Crepet WL (1983) The role of insect pollination in the evolution of the angiosperms. In:

Real L (ed) Pollination biology, pp 29-50. Academic Press, Orlando, FL Crepet WL (1984) Advanced (constant) insect pollination mechanisms: pattern of evolution and implications vis-à-vis angiosperm diversity. Ann Missouri Bot Gard 71:607-630

Crosby JL (1970) The evolution of genetic discontinuity: computer models of the selection of barriers to interbreeding between species. Heredity 25:253-297 Dieckmann U & Doebeli M (1999) On the origin of species by sympatric speciation. Nature 400:354-357

Dilley JD, Wilson P & Mesler MR (2000) The radiation of Calochortus: generalist flowers moving through a mosaic of potential pollinators. Oikos 89:209-222 Dodd ME, Silvertown J & Chase MW (1999) Phylogenetic analysis of trait evolution and species diversity variation among angiosperm families. Evolution 53:732-744 Dukas R & Ellner S (1993) Information processing and prey detection. Ecology


Endler JA (1977) Geographic variation, speciation, and clines. Princeton University Press, Princeton, NJ

Felsenstein J (1981) Skepticism towards Santa Rosalia, or why are there so few kinds of animals? Evolution 35:124-138 Fleming TH & Holland JN (1998) The evolution of obligate pollination mutualisms:

senita cactus and senita moth. Oecologia 114:368-375 Free JB (1966) The foraging behavior of bees and its effect on the isolation and speciation of plants. In: Hawkes JG (ed) Reproductive biology and taxonomy of vascular plants, pp 76-91. Pergamon Press, Oxford

Fulton M & Hodges SA (1999) Floral isolation between Aquilegiaformosa and A. pubescens.

Proc R Soc Lond B 266:2247-2252 Galen C (1996) Rates of floral evolution: adaptation to bumblebee pollination in an alpine wildflower, Polemonium viscosum. Evolution 50:120-125 Galen C, Zimmer KA & Newport ME (1987) Pollination in floral scent morphs of Polemonium viscosum: a mechanism for disruptive selection on flower size. Evolution 41:599-606

Goulson D & Jerrim K (1997) Maintenance of the species boundary between Silene dioica and S. latifolia (red and white campion). Oikos 79:115-126 Grant KA & Grant V (1964) Mechanical isolation of Salvia apiana and Salvia mellifera

(Labiatae). Evolution 18:196-212 Grant KA & Grant V (1967) Effects of hummingbird migration on plant speciation in the

California flora. Evolution 21:457-465 Grant V (1949) Pollination systems as isolating mechanisms in angiosperms. Evolution 3:82-97

Grant V (1952) Isolation and hybridization between Aquilegiaformosa and A. pubescens. Aliso 2:341-360

Grant V (1994) Modes and origins of mechanical and ethological isolation in angiosperms. Proc Natl Acad Sci USA 91:3-10 Grant V & Grant A (1960) Genetic and taxonomic studies in Gilia. XI. Fertility relationships of the diploid cobwebby gilias. Aliso 4:435-481 Grant V & Grant KA (1965) Flower pollination in the phlox family. Columbia University Press, New York

Grant V & Wilken DH (1988) Natural hybridization between Ipomopsis aggregata and I.

tenuituba (Polemoniaceae). Bot Gaz 149:213-221 Green DG (1994) Connectivity and complexity in landscapes and ecosystems. Pacif Cons Biol 3:194-200

Grimaldi D (1999) The co-radiations of pollinating insects and angiosperms in the

Cretaceous. Ann Missouri Bot Gard 86:373-406 Harrison RC (1990) Hybrid zones: windows on evolutionary processes. Oxf Surv Evol Biol 7:69-128

Herrera CM (1988) Variation in mutualisms: the spatiotemporal mosaic of a pollinator assemblage. Biol J Linn Soc 35:95-125 Herrera CM (1995) Microclimate and individual variation in pollinators: flowering plants are more than their flowers. Ecology 76:1516-1524 Herrera CM (1996) Floral traits and plant adaptation to insect pollinators: a devil's advocate approach. In: Lloyd DG & Barrett SCH (eds) Floral biology: studies on floral evolution in animal-pollinated plants, pp 65-87. Chapman & Hall, New York Hiesey WM, Nobs MS & Bjorkman O (1971) Experimental studies on the nature of species. V. Biosystematics, genetics and physiological ecology of the Erythranthe section of Mimulus. Carnegie Institution ofWashington, Washington DC, Publication 628

Hodges SA & Arnold ML (1994) Columbines: a geographically widespread species flock.

Proc Natl Acad Sci USA 91:5129-5132 Howard DJ & Berlocher SH (1998) Endless forms: species and speciation. Oxford University Press, New York

Hughes KW & Vickery RK Jr (1974) Patterns of heterosis and crossing barriers from increasing genetic distance between populations of the Mimulus luteus complex. J Genet 61:235-245

Hughes KW & Vickery RK Jr (1975) Evolutionary divergence in closely related populations of Mimulusguttatus (Scrophulariaceae). Great Basin Nat 35:240-244 Hughes RN (1979) Optimal diets under the energy maximization premise: the effects of recognition time and learning. Am Nat 113:209-221 Ippolito A & Holtsford T (1999) Selection of Nicotiana (Solanaceae) floral morphology in the wild. Abstr XVI IntBot Congr 442 Jones CE (1978) Pollinator constancy as a pre-pollination isolating mechanism between sympatric species of Cercidium. Evolution 32:189-198 Jordano P (1987) Patterns of mutualistic interactions in pollination and seed dispersal: connectance, dependence asymmetries, and coevolution. Am Nat 129:657-677 Kacelnik A & Bateson M (1996) Risky theories - the effects of variance on foraging decisions. Am Zool 36:402-434 Kearns CA, Inouye DW & Waser NM (1998) Endangered mutualisms: the conservation of plant-pollinator interactions. Ann RevEcol Syst 29:83-112 Kruckeberg A (1957) Variation in infertility of hybrids between isolated populations of the serpentine species Streptanthus glandulosus Hook. Evolution 11:185-211 Kunin WE & Iwasa Y (1996) Pollinator foraging strategies in mixed floral arrays: density effects and floral constancy. Theor Popul Biol 49:232-263 Kwak MM & Velterop O (1997) Flower visitation by generalists and specialists: analysis of pollinator quality. Proc Exp Appl Entomol Neth Entomol Soc 8:85-89 Leebens-Mack J & Milligan BG (1998) Pollination biology in hybridizing Baptisia

(Fabaceae) populations. Am J Bot 85:500-507 Leebens-Mack J, Pellmyr O & Brock M (1998) Host specificity and the genetic structure of two yucca moth species in a yucca hybrid zone. Evolution 52:1376-1382 Levin DA (1978) The origin of isolating mechanisms in flowering plants. Evol Biol 11:185-317

Lewis H & Epling C (1959) Delphiniumgypsophilum, a diploid species of hybrid origin. Evolution 13:511-525

Macior LW (1971) Co-evolution of plants and animals - systematic insights from plant-insect interactions. Taxon 20:17-28 May RM & Anderson RM (1987) Transmission dynamics of HIV infection. Nature 326:137-142

Maynard Smith J (1983) Current controversies in evolutionary biology. In: Grene M (ed)

Dimensions ofDarwinism, pp 273-286. Cambridge University Press, Cambridge McNair JN (1981) A stochastic foraging model with predator training effects. II. Optimal diets. Theor Popul Biol 9:147-162 Melendez-Ackerman EJ, Campbell DR & Waser NM (1997) Hummingbird behavior and mechanisms of selection on flower color in Ipomopsis. Ecology 78:2532-2541 Memmott J (1999) The structure of a plant-pollinator food web. Ecol Lett 2:276-280 Mitchell WA (1989) Informational constraints on optimally foraging hummingbirds. Oikos 55:145-154

Momose K, Yumoto T, Nagamitsu T, Kato M, Nagamasu H, Sakai S, Harrison RD, Itioka T, Hamid AA & Inoue T (1998) Pollination biology in a lowland dipterocarp forest in Sarawak, Malaysia. I. Characteristics of the plant-pollinator community in a lowland dipterocarp forest. Am J Bot 85:1477-1501 Müller H (1873) On the fertilisation of flowers by insect and on the reciprocal adaptation of both. Nature 8:187-189, 205-206 Oliver CG (1972) Genetic and phenotypic differentiation and geographic distance in four species of Lepidoptera. Evolution 26:221-241

Olsen KM (1997) Pollination effectiveness and pollinator importance in a population of

Heterotheca subaxillaris (Asteraceae). Oecologia 109:114-121 Otte D & Endler JA (1989) Speciation and its consequences. Sinauer, Sunderland, MA Parker GA & Maynard Smith J (1990) Optimality theory in evolutionary biology. Nature 348:27-33

Patel A, Hossaert-McKey M & McKey D (1993) Ficus-pollinator research in India: past, present and future. Curr Sci 65:243-253 Paterniani E (1969) Selection for reproductive isolation between two populations of maize, Zea mays L. Evolution 23:534-547 Pijl L van der (1960) Ecological aspects of flower evolution. I. Phyletic evolution. Evolution 14:403-416

Pijl L van der (1961) Ecological aspects of flower evolution. II. Zoophilous flower classes. Evolution 15:44-59

Powell JA (1992) Interrelationships of yuccas and yucca moths. Trends Ecol Evol 7:10-15 Pyke GH (1984) Optimal foraging theory: a critical review. Ann Rev Ecol Syst 15:523-575 Riesberg LH (1995) The role of hybridization in evolution: old wine in new skins. Am] Bot 82:944-953

Riesberg LH, Desrochers AM & Youn SJ (1995) Interspecific pollen competition as a reproductive barrier between sympatric species of Helianthus (Asteraceae). Am] Bot 82:515-519

Schemske DW & Bradshaw HD Jr (1999) Pollinator preference and the evolution of floral traits in monkey flowers (Mimulus). Proc Natl Acad Sci USA 96:11910-11915 Smallwood PD (1996) An introduction to risk sensitivity: the use of Jensen's inequality to clarify evolutionary arguments of adaptation and constraint. Am Zool


Stebbins GL (1970) Adaptive radiation of reproductive characteristics in angiosperms. I.

Pollination mechanisms. Ann Rev Ecol Syst 1:307-326 Stephens DW & Krebs JR (1986) Foraging theory. Princeton University Press, Princeton, NJ Straw RM (1956) Floral isolation in Penstemon. Am Nat 90:47-53 Sutherland SD & Vickery RK Jr (1993) On the relative importance of floral color, shape, and nectar rewards in attracting pollinators to Mimulus. Great Basin Nat


Templeton AR (1981) Mechanisms of speciation - a population genetic approach. Ann Rev Ecol Syst 12:23-48

Vickery RK Jr (1978) Case studies in the evolution of species complexes in Mimulus. Evol Biol 11:405-507

Vickery RK Jr (1995) Speciation in Mimulus, or, can a simple flower color mutant lead to species divergence? Great Basin Nat 55:177-180 Waser NM (1986) Flower constancy: definition, cause, and measurement. Am Nat


Waser NM (1998) Pollination, angiosperm speciation, and the nature of species boundaries. Oikos 82:198-201 Waser NM & Chittka L (1998) Bedazzled by flowers. Nature 394:835-836 Waser NM & Price MV (1993) Crossing distance effects on prezygotic performance in plants: an argument for female choice. Oikos 68:303-308 Waser NM & Price MV (1998) What plant ecologists can learn from zoology. Persp Plant

Ecol Evol Syst 1:137-150 Waser NM, Chittka L, Price MV, Williams N & Ollerton J (1996) Generalization in pollination systems, and why it matters. Ecology 77:279-296

Waser NM, Price MV & Shaw RG (2000) Outbreeding depression varies among cohorts of Ipomopsis aggregata planted in nature. Evolution 54:485-491 Wcislo WT & Cane JH (1996) Floral resouce utilization by solitary bees (Hymenoptera: Apoidea) and exploitation of their stored foods by natural enemies. Ann Rev Entomol 41:257-286 Webber JM (1960) Hybridization and instability of Yucca. Madroño 15:187-192 Wells H, Wells PH & Smith DM (1983) Ethological isolation of plants. I. Colour selection by honeybees. J Apic Res 22:33-44 Werth E (1955) Ist die Pollen-übertragung durch Insekten geeignet, die zur Artbildung nötige (mechanische) Isolierung zu fördern? Ber Deut Bot Ges 68:163-166 Wesselingh RA & Arnold ML (2000) Pollinator behaviour and the evolution of Louisiana iris hybrid zones. J Evol Biol 13:171-180 Wilson P & Thomson JD (1996) How do flowers diverge? In: Lloyd DG & Barrett SCH (eds) Floral biology: studies on floral evolution in animal-pollinated systems, pp 88-111. Chapman & Hall, New York Wolf PG & Soltis PS (1992) Estimates of gene flow among populations, geographic races, and species in the Ipomopsis aggregata complex. Genetics 130:639-647 Wolf PG, Soltis PS & Soltis DE (1991) Genetic relationships and patterns of allozymic divergence in the Ipomopsis aggregata complex and related species (Polemoniaceae). Am J Bot 78:515-526 Wolf PG, Soltis PS & Soltis DE (1993) Phylogenetic relationships of the Ipomopsis aggregata complex and related species (Polemoniaceae): evidence from chloroplast DNA restriction site variation. Syst Bot 18:652-662 Wolf PG, Murray RA & Sipes SD (1997) Species-independent, geographical structuring of chloroplast DNA haplotypes in a montane herb Ipomopsis (Polemoniaceae). Mol Ecol 6:283-291

Wolf PG, Campbell DR, Waser NM, Sipes SD, Toler TR & Archibald JK (2001) Tests of pre- and post-pollination barriers to hybridization between sympatric species of Ipomopsis (Polemoniaceae). Am J Bot, in press Wolf TJ, Schmid-Hempel P, Ellington CP & Stevenson RD (1989) Physiological correlates of foraging efforts in honey-bees; oxygen consumption and nectar load. Func Ecol


Was this article helpful?

0 0

Post a comment