Abstract:
We present a phylogenetic comparative study assessing the evolutionary
determinants of egg size in the moth family Geometridae. These moths were
found to show a strong negative allometric relationship between egg size and
maternal body size. Using recently developed comparative methods based on
an Ornstein-Uhlenbeck process, we show that maternal body size explains
over half the variation in egg size. However, other determinants are less clear:
ecological factors, previously hypothesized to affect egg size, were not found to
have a considerable influence in the Geometridae. The limited role of such
third factors suggests a direct causal link between egg size and body size rather
than an indirect correlation mediated by some ecological factors. Notably, no
large geometrid species lay small eggs. This pattern suggests that maternal
body size poses a physical constraint on egg size, but within these limits, there
appears to be a rather invariable selection for larger eggs.
