Insect Egg Size and Shape Evolve With Ecology but Not Developmental Rate

Abstract

Over the course of evolution, the size of life changes dramatically. These changes are thought to be explained by developmental, morphological, and ecological pressures. To perform phylogenetic tests of these hypotheses, we generated a dataset of more than ten thousand descriptions of insect eggs, and combined these with genetic and life-history datasets. We show that across eight orders of magnitude in egg volume variation, the relationship between size and shape itself evolves, such that predicted global patterns of scaling do not adequately explain egg shape diversity. We show that size is not correlated with developmental rate, and that for many insects, egg size is not correlated with adult body size either. Instead, we find that the evolution of parasitoidism and aquatic oviposition help to explain the size and shape diversification. Our study suggests that where eggs are laid, rather than universal allometric constants, underlies size and shape evolution.