Meeting Abstract
Major shifts in life history evolution – such as the transition from pre- to post-fertilization maternal provisioning in viviparous organisms – require complex morphological and physiological adaptations. The conditions under which these striking transitions arise remain unknown. Theory postulates that parent-offspring conflict can drive diversification in maternal provisioning strategies, but alternative hypotheses focusing on sexual selection and ecological adaptation have been neglected. We use comparative phylogenetic methods with 94 species in the family Poeciliidae to show that repeated shifts from lecithotrophy (pre-fertilization provisioning) to matrotrophy (post-fertilization provisioning) preceded concomitant changes in sexual selection, establishing a previously missing causal link between shifts in life history and mating systems. Bi-directional evolution along the lecithotrophy-matrotrophy continuum is not consistent with conflict hypotheses that predict ever increasing levels of matrotrophy once post-fertilization provisioning evolved. We also showed that variation in matrotrophy was correlated with high primary productivity and low competition, consistent with predictions of theoretical models of ecological adaptation. We propose a novel paradigm of matrotrophy evolution, emphasizing interactions between conflict-mechanisms and ecological sources of selection. Specifically, natural selection mediated by resource availability may counterbalance evolutionary trends mediated by parent-offspring conflicts. Under this paradigm, bi-directional evolution in maternal provisioning strategies is a mere consequence of shifting balances between natural selection favoring lecithotrophy and conflict-fueled increases in matrotrophy.
