Purging of inbreeding depression within a population of Oxalis alpina (Oxalidaceae)

Variation among individuals in levels of inbreeding depression associated with selfing levels could influence mating system evolution by purging deleterious alleles, but empirical evidence for this association is limited.

We investigated the association of family-level inbreeding depression and presumed inbreeding history in a tristylous population of Oxalis alpina (Oxalidaceae).

Mid-styled individuals possessed the greatest degree of self-compatibility (SC) and produced more autogamous capsules than short- or long-styled individuals. Offspring of highly self-compatible mid-styled individuals showed reduced inbreeding depression. Mid-styled plants that produced capsules autogamously exhibited reduced stigma-anther separation compared to mid-styled plants that produced no capsules autogamously. Reduced inbreeding depression was not correlated with stigma-anther separation, suggesting that self-compatibility and autogamy evolve before morphological changes in stigma-anther separation.

Purging of inbreeding depression occurred in SC mid-styled maternal families. Low inbreeding depression in SC mid-styled plants may lead to retention of the mid-styled morph in populations, despite the occurrence of higher selfing rates in mid-styled relative to short- or long-styled morphs. Variation among individuals in levels of self-fertilization within populations may lead to associations between inbreeding lineages and lower levels of inbreeding depression, influencing the evolution of mating systems.