Evidence for inbreeding depression and post-pollination selection against inbreeding in the dioecious plant Silene latifolia

Abstract

In many species, inbred individuals have reduced fitness. In plants with limited pollen and seed dispersal, post-pollination selection may reduce biparental inbreeding, but knowledge on the prevalence and importance of pollen competition or post-pollination selection after non-self pollination is scarce. We tested whether post-pollination selection favours less related pollen donors and reduces inbreeding in the dioecious plant Silene latifolia. We crossed 20 plants with pollen from a sibling and an unrelated male, and with a mix of both. We found significant inbreeding depression on vegetative growth, age at first flowering and total fitness (22% in males and 14% in females). In mixed pollinations, the unrelated male sired on average 57% of the offspring. The greater the paternity share of the unrelated sire, the larger the difference in relatedness of the two males to the female. The effect of genetic similarity on paternity is consistent with predictions for post-pollination selection, although paternity, at least in some crosses, may be affected by additional factors. Our data show that in plant systems with inbreeding depression, such as S. latifolia, pollen or embryo selection after multiple-donor pollination may indeed reduce inbreeding.

The effects of inbreeding, genetic dissimilarity and phenotype on male reproductive success in a dioecious plant

“…The microsatellite loci were isolated by Ecogenics GmbH (Zurich, Switzerland; see electronic supplementary material, Figure 1. Experimental design comparing the emergent predictors between the present study and the previous one [15]. Here, inbred and outbred plants obtained previously [15] were exposed to natural pollination in a common garden in order to address inbreeding depression for siring success and the effects of genetic dissimilarity between mates, donor phenotype and spatial proximity on paternity success under realistic conditions of natural pollination with variable size and composition of pollen loads.…”

“…(b) Structure of experimental population As described in Teixeira et al [15], we conducted controlled crosses to generate inbred and outbred plants from seeds collected from fruits in a natural population in Village-Neuf (France, 47836 0 25 00 N; 7833 0 31 E; 245 m a.s.l.). Twenty female plants were pollinated by a brother (from the same field-collected fruit as the female plant, i.e.…”

“…Using controlled crosses, we have shown previously that inbreeding depression affects many vegetative and reproductive traits in the dioecious white campion, Silene latifolia, and that genetic dissimilarity between mates affected siring success in hand pollination competition with two donors [15]. However, to our knowledge there is no study that has assessed whether male reproductive success in plants is directly affected by the levels of inbreeding, in particular, under conditions of natural interaction with pollinators and mixed pollen loads [1].…”

“…By exposing inbred and outbred plants generated previously [15] to natural pollinators, we specifically ask whether siring success is affected by (i) levels of inbreeding in males, (ii) male -female relatedness, and (iii) male phenotypic traits, including sexually dimorphic and gametophytic traits.…”

“…Founder populations appear as a consequence of occasional long-distance seed dispersal and consist of sibships from few or single fruits. This creates a unit of plants sufficiently large to be visible to pollinators [36], but increases the risk of inbreeding [15,34]. However, it is unknown whether inbred S. latifolia males suffer reduced fecundity under natural pollination.…”