Unification and generalization of models of zygote survival

Abstract

Mathematical models linking zygote size to survival until maturity are central to evolutionary ecology, yet many existing formulations remain fragmented and conceptually disconnected. These models fall broadly into two categories: phenomenological models, which lack explicit biological justification, and those grounded in survival analysis, which we, in contrast to phenomenological models, call mechanistic models. Although the latter are theoretically preferable, many commonly used mechanistic functions lack a common basis despite being better integrated than phenomenological models, and some are known to contain inconsistent dimensional assumptions. Here, we use a general framework that links zygote survival functions to growth dynamics and size-dependent mortality to show that many existing zygote survival models are corollaries of allometric growth models and generalize readily to account for allometric mortality, revealing previously hidden connections among models. The unification presented here provides principled grounds for re-evaluating the parameters and predictions of existing models.