Rosengren F, Cronberg N, Hansson B
Biodiversity, Department of Biology, Lund University, Lund, Sweden.
Molecular Ecology and Evolution Lab, Department of Biology, Lund University, Lund, Sweden.
Heredity (Edinb). 2016 Jan;116(1):107-13. doi: 10.1038/hdy.2015.79. Epub 2015 Sep 2.
Epiphytic dwarf males on the females present a possible solution to the problem of short fertilization distances in mosses. However, leptokurtic spore dispersal makes dwarf males likely to be closely related to their host shoot, with an accompanying risk of inbreeding. The capacity of a female to harbour a high number of different dwarf males suggests that there may be mechanisms in place that counteract inbreeding, such as polyandry and post-fertilization selection. We have genotyped sporophytes, female host shoots and dwarf males in four populations of the moss Homalothecium lutescens. We found no evidence of selective sporophyte abortion based on level of heterozygosity. The occurrence of entirely homozygous sporophytes together with significantly positive inbreeding coefficients in three of the populations (mean FIS between 0.48 and 0.64) suggest frequent mother-son mating events. However, 23% of all sampled sporophytes had a higher level of heterozygosity compared with the mean expected heterozygosity at the population level. Polyandry was frequent, on average 59% of the sporophytes on a female shoot were sired by distinct fathers. In conclusion, sporadic fertilizations by dwarf males originating from nonhost female shoots appear to counteract strong inbreeding.
雌性植株上的附生矮化雄性个体为解决苔藓受精距离短的问题提供了一种可能的途径。然而，尖峰态的孢子扩散使得矮化雄性个体与其宿主枝条可能存在密切的亲缘关系，随之而来的是近亲繁殖的风险。雌性植株容纳大量不同矮化雄性个体的能力表明，可能存在一些机制来抵消近亲繁殖，比如多配偶制和受精后选择。我们对藓类植物淡黄异萼苔四个种群中的孢子体、雌性宿主枝条和矮化雄性个体进行了基因分型。我们没有发现基于杂合度水平的选择性孢子体败育的证据。在三个种群中出现了完全纯合的孢子体，同时近亲繁殖系数显著为正（平均固定指数在0.48至0.64之间），这表明存在频繁的母子交配事件。然而，在所有采样的孢子体中，有23%的杂合度水平高于种群水平的平均预期杂合度。多配偶制很常见，平均而言，雌性枝条上59%的孢子体是由不同的父本受精产生的。总之，来自非宿主雌性枝条的矮化雄性个体的零星受精似乎抵消了强烈的近亲繁殖。
