What Keeps Insects Small? Time Limitation during Oviposition Reduces the Fecundity Benefit of Female Size in a Butterfly

Abstract

Laboratory studies of insects suggest that female fecundity may increase very rapidly with adult size and that mass may often increase close to exponentially with time during larval growth. These relationships make it difficult to see how realistic levels of larval mortality can outweigh the fecundity benefit of prolonged growth. Hence, it is unclear why many insects do not become bigger. In this study, we experimentally explore the relationship between female size and fecundity in the butterfly Pararge aegeria and show that thermally induced time limitation during oviposition may substantially reduce the fecundity benefit of larger females. We model time-limited oviposition under natural temperature conditions and show that fecundity is also likely to increase asymptotically with female size in the field. With realistic estimates of juvenile mortality, the model predicts optimal body sizes within the observed range even when larvae grow exponentially. We conclude that one important reason for why insects with a high capacity of larval growth do not evolve toward larger sizes may be that the fecundity benefit is in fact relatively limited under natural conditions. If so, these results may help resolve some of the inconsistencies between theory and empirical patterns in explaining optimal size in insects.

Phenological asynchrony between herbivorous insects and their hosts: signal of climate change or pre-existing adaptive strategy?

“…(a) The bay checkerspot Post-diapause larvae of the bay checkerspot that were programmed to mature earlier and take less risk of offspring mortality from host senescence would of necessity become smaller adults and suffer a fitness cost from reduced fecundity (Boggs 1997;Gotthard et al 2007;Neve & Singer 2008; but see Reznick et al 2000 for discussion of exceptions to this style of logic). Conversely, those programmed to grow large would prolong larval development and benefit from high fecundity at the cost of high risk of mortality for their offspring.…”

“…If we assume that about a third of this weight gain would go towards egg production (cf. Gotthard et al 2007); this would amount to around 200 additional eggs.…”

Mothers Matter Too: Benefits of Temperature Oviposition Preferences in Newts

“…However, temperature oviposition preferences seem equally important for female performance, especially in species with a prolonged egg-laying period in temperate areas. Seasonal time constraints can favor high oviposition rates [13]. Oviposition rates are temperature-dependent [13], [14], and thus it seems likely that time-limited females prefer particular temperatures for oviposition primarily to maximize their egg-laying performance.…”

The diapause decision as a cascade switch for adaptive developmental plasticity in body mass in a butterfly

“…As thermal conditions during these two periods differ substantially (Fig. 1) life history models predicts that optimal female mass is significantly smaller in May conditions than in conditions typical of June (Gotthard et al. , 2007; Berger et al.…”