Parental guarding behaviour affects the evolution of egg shapes

When females guard clutches on substrates against predators with a straddling posture, eggs located in the peripheral area of such clutches experience high predation pressure.Thus, selection may favor compact clutches composed of longitudinally elongated eggs.We tested this hypothesis using shield bugs.Our phylogenetic comparative analyses revealed that eggs were more elongated in caring than in non-caring species, although this difference was obscured in species with large eggs.Reconstructed ancestral states of egg shape and maternal care suggested that the enhanced elongation of eggs occurred after the establishment of maternal care.