Energetics of reproduction: consequences of divergent selection on egg size, food limitation, and female age for egg composition and reproductive effort in a butterfly

Abstract

Using lines artificially selected on egg size and being subjected to a restricted and an unrestricted feeding treatment, we examined the relationships between egg size, egg number, egg composition, and reproductive investment in the butterfly Bicyclus anynana. Despite a successful manipulation of egg size, correlated responses to selection in larval time, pupal mass, pupal time, longevity, fecundity, or the amount of energy allocated to reproduction were virtually absent. Thus, there was no indication for an evolutionary link between offspring size and reproductive investment. Egg composition, in contrast, was affected by selection, with larger eggs containing relatively more lipid and water, but less protein and energy compared to smaller eggs. Hence, females producing large eggs did not have to sacrifice fecundity due to adjustments in egg composition. Food limitation per se caused only minor changes in egg composition, and there was no general reduction in egg provisioning with female age. The latter was restricted to food‐limited females, whereas egg quality remained remarkably similar throughout the females’ life in control groups. We conclude that neglecting changes in biochemical egg composition, depending on genetic background, food availability, and female age, may introduce substantial error when estimating reproductive effort, and may ultimately lead to invalid conclusions. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 403–418.

Maternal Body Size as an Evolutionary Constraint on Egg Size in a Butterfly

“…Relative egg water content remained invariant across selection regimes (Table 1), contrasting with the previous results showing that larger eggs contain relatively more water (Fischer et al 2006; Karl et al 2007). Again, this difference is likely to be attributable to the much larger variation in egg size in the earlier studies.…”

“…The slight decrease in egg size with female age probably reflects resource depletion (Begon and Parker 1986; Karlsson 1987; Giron and Casas 2003). Overall, this decline in egg size was very small in this study, likely reflecting the beneficial feeding conditions and the strong dependence of B. anynana on adult‐derived nutrients (income breeding; Tammaru and Haukioja 1996; Fischer et al 2004; Bauerfeind and Fischer 2005b; Karl et al 2007). Fischer et al (2006) found a steeper decrease in large compared to small single‐trait egg‐selected lines, which might be the result of a much higher variation in egg size.…”

Phylloplane bacteria increase the negative impact of food limitation on insect fitness

“…This is in agreement with results from the forest tent caterpillar Malacosoma disstria (Colasurdo et al, 2009). In a study on another lepidopteran, Bicyclus anynana Butler, selection for increased egg size was associated with increased lipid and water, but with a reduction in protein and energy, suggesting that females could balance egg provisioning and fecundity (Karl et al, 2007). However, both had a clear positive relationship with increasing egg size, indicating that egg size and composition can be related in Lepidoptera.…”

Food stress sensitivity and flight performance across phosphoglucose isomerase enzyme genotypes in the sooty copper butterfly

“…Note that, despite the increase in development time, larvae were not able to fully compensate for the period of starvation, as pupal mass in foodstressed individuals was nevertheless lower compared to controls (see also Blanckenhorn 1999;Bauerfeind and Fischer 2005;Karl et al 2007). Sex-specific differences in life-history traits were found in larval development time, growth rate and pupal mass, but not in pupal development time.…”