Heterozygote excess in a self‐incompatible and partially clonal forest tree species —Prunus avium L.

Abstract

Wild cherry (Prunus avium L.), a partially asexual self-incompatible forest tree, shows heterozygote excess, which is a poorly studied phenomenon. In three natural populations, we found significant heterozygote excess at almost all investigated loci (eight microsatellites and markers for the self-incompatibility locus). We examined four hypotheses to account for this observed heterozygote excess. First, negative F(IS) can result from a lack of selfed progeny in small populations of outcrossing species. A second explanation for negative F(IS) is selection during the life cycle of the most heterozygous individuals. A third explanation is negative assortative mating when reproduction occurs between individuals bearing phenotypes more dissimilar than by chance. The last explanation for negative F(IS) relies on asexual reproduction. Expectations for each hypothesis were tested using empirical data. Patterns of F(IS) differed among loci. Nevertheless, our experimental results did not confirm the small sample size hypothesis. Although one locus is probably under a hitch-hiking effect from the SI locus, we rejected the effect of the self-incompatibility locus for the genome as a whole. Similarly, although one locus showed a clear pattern consistent with the selection of heterozygous individuals, the heterosis effect over the whole genome was rejected. Finally, our results revealed that clonality probably explains significant negative F(IS) in wild cherry populations when considering all individuals. More theoretical effort is needed to develop expectations and hypotheses, and test them in the case of species combining self-incompatibility and partially asexual reproduction.

Clonal structure and high genetic diversity at peripheral populations of Sorbus torminalis (L.) Crantz.

“…Our results confirmed this finding with inbreeding coefficients being consistently slightly negative across almost all SSR loci. This is reasonable given the self-incompatibility mating system of the species (Ludwig et al 2013, Stoeckel et al 2006; however, asexual reproduction may also affect FIS estimates (Stoeckel & Masson 2014).…”

Microsatélites revelan heterocigosidad y estructura poblacional de murciélagos vampiro (Desmodus rotundus) (Quiróptera: Phyllostomidae) de México

“…Heterozygosity excess has been appointed to several causes (Stoeckel et al, 2006): 1) May possibility the result from small reproductive populations, where only few breeders have real fitness. 2) Outbreeding may be result of selective forces of the most heterozygous individuals.…”

Contemporary pollen flow, characterization of the maternal ecological neighbourhood and mating patterns in wild cherry (Prunus avium L.)

“…Theoretical models predict that high levels of polymorphism will be maintained at the S locus through frequencydependant selection as rare alleles theoretically have a higher probability of successfully pollinating other individuals (Wright, 1939;Campbell and Lawrence, 1981). In natural wild cherry populations, the distribution and frequency of S alleles is therefore likely to be of major ecological significance (Schueler et al, 2006;Stoeckel et al, 2006). Self-incompatibility is strongly associated with clonal reproduction and it is likely that clonality provides reproductive assurance (Vallejo-Marín and O'Brien, 2007).…”

“…Self-incompatibility is strongly associated with clonal reproduction and it is likely that clonality provides reproductive assurance (Vallejo-Marín and O'Brien, 2007). Asexual reproduction is also common in wild cherry (Stoeckel et al, 2006;Vaughan et al, 2007b) and the presence of clonal groups will probably influence both pollen receipt and production as seen in other species (Handel, 1985).…”