A general stochastic model for sporophytic self-incompatibility

TL;DR

This paper develops a stochastic model to understand how self-incompatibility affects the extinction risk of flowering plant populations, highlighting conditions where such species are more resilient or vulnerable.

Contribution

It introduces a general stochastic framework for self-incompatibility, focusing on distylous plants, and analyzes extinction probabilities in small populations.

Findings

Self-incompatible species can be less prone to extinction in large populations.

Pollen limitation impacts extinction risk differently in self-incompatible versus self-fertile species.

The model provides conditions where self-incompatibility either mitigates or exacerbates extinction risk.

Abstract

Disentangling the processes leading populations to extinction is a major topic in ecology and conservation biology. The difficulty to find a mate in many species is one of these processes. Here, we investigate the impact of self-incompatibility in flowering plants, where several inter-compatible classes of individuals exist but individuals of the same class cannot mate. We model pollen limitation through different relationships between mate availability and fertilization success. After deriving a general stochastic model, we focus on the simple case of distylous plant species where only two classes of individuals exist. We first study the dynamics of such a species in a large population limit and then, we look for an approximation of the extinction probability in small populations. This leads us to consider inhomogeneous random walks on the positive quadrant. We compare the dynamics of distylous species to self-fertile species with and without inbreeding depression, to obtain the conditions under which self-incompatible species could be less sensitive to extinction while they can suffer more pollen limitation.