Early inbreeding depression in the sexually polymorphic plant Dianthus sylvestris (Caryophyllaceae): Effects of selfing and biparental inbreeding among sex morphs

Predominantly outcrossing plant species are expected to accumulate recessive deleterious mutations, which can be purged when in a homozygous state following selfi ng. Individuals may vary in their genetic load because of different selfi ng histories, which could lead to differences in inbreeding depression among families. Lineage-dependent inbreeding depression can appear in gynodioecious species if obligatory outcrossed females are more likely to produce female offspring and if partially selfi ng hermaphrodites are more likely to produce hermaphrodites. We investigated inbreeding depression at the zygote, seed, and germination stages in the gynomonoecious-gynodioecious Dianthus sylvestris , including pure-sexed plants and a mixed morph. We performed handpollinations on 56 plants, belonging to the three morphs, each receiving 2 – 3 cross treatments (out-, sib- and self-pollination) on multiple fl owers. Effects of cross treatments varied among stages and infl uenced seed provisioning, with sibling competition mainly occurring within outcrossed fruits. We found signifi cant inbreeding depression for seed mass and germination and cumulative early inbreeding depression varied greatly among families. Among sex morphs, we found that females and hermaphrodites differed in biparental inbreeding depression, whereas uniparental was similar for all. Signifi cant inbreeding depression levels may play a role in female maintenance in this species, and individual variation in association with sex-lineages proclivity is discussed.