Plasticity in Butterfly Egg Size: Why Larger Offspring at Lower Temperatures?

Abstract

Dividing sister pairs of the butterfly Bicyclus anynana (reared in a common environment) between high and low temperature shows that oviposition temperature induces a plastic response in egg size. Females at a lower temperature laid significantly larger (but fewer) eggs than their sisters kept at a higher temperature, whereas total reproductive investment increased with temperature. Cross‐transfer experiments demonstrated that this plastic response in egg size is reversible. Interestingly, this pattern parallels an almost universal temperature‐induced developmental response in ectotherm body size. In both cases, however, we do not yet understand the underlying mechanisms or the potential adaptive significance. By cross‐transferring the experimentally manipulated eggs between temperatures, we showed that the larger eggs produced at a lower temperature had a higher hatching success, and yielded larger hatchlings with a slightly higher probability of reaching maturity and shorter larval development time (at the lower temperature) compared to the smaller eggs produced at a higher temperature. Overall, the lower temperature was slightly more detrimental for smaller than for larger eggs. The slight differences in survival across temperatures, together with more substantial differences in fecundity, indicate that it could pay off to produce fewer but larger offspring (with increased fitness) at a lower temperature, but more and smaller offspring at a higher temperature where offspring survival was generally high. Our data present for the first time evidence that selection may favor larger eggs at a lower temperature, and thus that a plastic response of egg size to temperature in ectotherms could be adaptive.

Cooler butterflies lay larger eggs: developmental plasticity versus acclimation

“…The rate of decrease was apparently very similar at both oviposition temperatures, as was found in a previous study using B. anynana (Fischer et al 2003a). Consequently, it is highly unlikely that differences in physiological age between oviposition temperatures confounded any of the results presented here.…”

Repeatability of egg size in two marine gastropods: brood order and female size do not contribute to intraspecific variation

“…It was suggested in each study that the observed decreases in egg size were due to reduction in adult size resulting from limited feeding after the onset of reproduction, or the detrimental effects of aging. Similar decreases in propagule size with age have been reported for shortlived terrestrial species including the housefly (McIntyre & Gooding 2000), a parasitic wasp (Giron & Casas 2003), some butterflies (Fischer et al 2003), and 8 weedy herbaceous plants (Cavers & Steel 1984). Egg size has occasionally been reported to increase with age in arthropods (e.g.…”

Developmental plasticity and acclimation both contribute to adaptive responses to alternating seasons of plenty and of stress in Bicyclus butterflies

“…Thus, when females reared in the laboratory at cool or warm temperatures, as experienced in the fi eld by larval cohorts of the dry or wet season form, begin to oviposit, they lay larger (but fewer) or smaller eggs, respectively (Fischer et al 2003a, b). By also using cross-transferring of females among low or high oviposition temperatures it is clear that they then acclimatize over about 10 days and change their egg size to that characteristic of the prevailing environment.…”