Data from: The evolutionary enigma of mixed mating systems in plants: occurrence, theoretical explanations, and empirical evidence

Mixed mating, in which hermaphrodite plant species reproduce by both self-
and cross-fertilization, presents a challenging problem for evolutionary
biologists. Theory suggests that inbreeding depression, the main selective
factor opposing the evolution of selfing, can be purged with
self-fertilization, a process that is expected to yield pure strategies of
either outcrossing or selfing. Here we present updated evidence suggesting
that mixed mating systems are frequent in seed plants. We outline the
floral and pollination mechanisms that can lead to intermediate
outcrossing, review the theoretical models that address the stability of
intermediate outcrossing, and examine relevant empirical evidence. A
comparative analysis of estimated inbreeding coefficients and outcrossing
rates suggests that mixed mating often evolves despite strong inbreeding
depression. The adaptive significance of mixed mating has yet to be fully
explained for any species. Recent theoretical and empirical work suggests
that future progress will come from a better integration of studies of
floral mechanisms, genetics, and ecology, and recognition of how selective
pressures vary in space and time.