Zygote survival functions: A critical systematisation

Abstract The life cycle of a sexually reproducing species starts from the formation of a zygote by fusion of two gametes. In external fertilisers, the survival of an individual organism from a zygote to an adult is precarious and depends largely on the gametic provisioning of resources by its parents (via the female gamete in species where anisogamy has evolved). In evolutionary ecology, this early survival time has been modelled using a variety of zygote survival functions . In evolutionary modelling applications, the fitness of an individual is measured by the number of its offspring that survive to reproductive maturity, making the survival probability of the offspring a key component in these models. Despite their significance, the existing zygote survival functions remain scattered, with little consensus on their theoretical principles and mathematical tools. Here, our aim was to provide clarification and coherence for future theoretical and empirical research. We achieve this by reconstructing the history of zygote survival modelling, analysing existing zygote survival functions and discussing their theoretical details and problems. Systematising existing survival functions will facilitate future modelling work and will decrease duplication of efforts by concentrating theoretical focus into a unified modelling discourse.