Wing Loss and Life History Tradeoffs

Food abundance and quality cannot be divorced from wing morphology because it is costly to produce and maintain the wings and their muscular and cuticular support (Roff and Fairbairn, 1991); insect flight muscle is one of the most metabolically active tissues known (e.g., Weis-Fogh, 1967). Flight behavior is also energetically demanding, and can alter the composition of hemolyph for up to 24 hr afterward in P. americana (King et al., 1986). These metabolic expenses place a significant demand on an insect's overall energy budget, and compete with other physiologically demanding life history processes. The best documented of these is egg production. Any easing of the selective pressure to maintain wings allows a female to divert more resources to egg production, increasing her fitness more than if she remained volant ("flight-oogen-esis syndrome") (Roff, 1986, 1990; Roff and Fairbairn,

1991). Flight capability can diminish rapidly under the right conditions (Denno et al., 1991; Marooka and Tojo,

1992), and may account for the lack of functional flight muscle in laboratory-reared females of Periplaneta (Table 2.1). The flight-oogenesis syndrome also may account for the prevalence of flightless females, rather than males, in cockroach species exhibiting sexual dimorphism in flight ability. The relationship between wing morphology and fecundity has been demonstrated in a number of insect species, including orthopteroids (e.g., Cisper et al., 2000), but is as yet unstudied in cockroaches. The fact that there are numerous cockroach species with males possessing reduced or absent wings suggests that there is a cost to the retention of wings even in males. In some insects, short-winged males have a mating advantage over macropter-ous males, or a gain in testes and body size (Dingle, 1996; Langellotto et al., 2000). Macroptery in males is most often related to the distribution of females in the habitat, and whether they are accessible to males on foot (Roff,

1990; Denno et al., 2001a). This is likely the case in cockroaches, because in many species females produce volatile sex pheromones; males use these chemical cues to actively seek mating partners (Gemeno and Schal, 2004). The degree of wing development may affect longevity in both sexes (Kaitala and Hulden, 1990; Roff and Fairbairn, 1991). It may be relevant, then, that among the longest-lived of the known cockroaches are apterous species that burrow in wood or soil (Chapter 3).

Was this article helpful?

0 0

Post a comment