Inbred women in a small and isolated Swiss village have fewer children

Despite overwhelming evidence for a negative effect of inbreeding on fitness in plants and nonhuman animals, the exact nature of its effect in humans remains subject to debate. To obtain a better understanding of the effects of inbreeding on reproductive success in humans, we reconstructed the genealogies of the current inhabitants of a small and isolated Swiss village and used these to estimate the level of inbreeding of both members of all married couples, as well as their relatedness (i.e. the level of inbreeding of their offspring). Although there was no effect of parental relatedness on the number of children a couple had, we found that inbred mothers, but not inbred fathers, had significantly fewer children. Thus, although related couples did not have fewer children themselves, their inbred daughters did leave them with fewer grandchildren. Thereby, we provide evidence for the existence of inbreeding depression in human fertility, also in relatively outbred and egalitarian communities.     

Inbreeding depression in Vriesea gigantea,a perennial bromeliad from southern Brazil

Inbreeding depression is a reduction of fitness in the progeny of closely related individuals and its effects are assigned to selfing or biparental inbreeding. Vriesea gigantea is a self‐compatible bromeliad species distributed in the Brazilian Atlantic rainforest and habitat destruction and fragmentation and collection have decreased the natural populations. We aim to describe the occurrence of inbreeding depression (δ) in three natural populations of V. gigantea and to correlate this phenomenon with previous studies of fertility, genetic diversity, population genetic structure, gene flow, mating system and seed dispersal in this species. Fifty‐four adult plants were sampled and 108 flowers were used for pollination treatments (selfing, outcrossing and control). For adult plants, we analysed plant and inflorescence height, flower numbers and seed set. In the progenies, evaluated parameters included seed germination and seedling survival rate. The results indicated low to moderate levels of inbreeding depression in V. gigantea (δ = 0.02 to 0.39), in agreement with molecular data from a previous study. Vriesea gigantea populations tolerate some degree of inbreeding, which is consistent with previous results on fertility, mating system, genetic diversity and gene flow. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 312–319.