Propensity for selfing varies within a population of hermaphroditic snails: coexistence of selfers, outcrossers, and mixed-mating individuals

To understand mating-system evolution in self-compatible hermaphrodites, variation in selfing rates is highly relevant. Empirical studies are rarely designed to capture variation between individuals, instead often comparing species and populations. Yet, evolution primarily occurs within populations, rendering among-individual variation essential. 
Observed individual selfing rates depend on the environment (e.g., differences in mate availability) and individuals’ propensity for selfing. We quantified individual variation in selfing propensity in the snail Radix balthica by conducting laboratory mating trials that manipulated mate availability (low vs. moderate) and estimating selfing rates from progeny arrays. We also measured female lifetime fitness. We found substantial among-individual variation in selfing propensity, including pure selfers (32%), pure outcrossers (31%), and mixed-mating individuals that selfed and outcrossed (37%). Experimental levels of mate availability did not si..., , ,