Evolution and biogeography of alpine apomictic plants

Abstract

AbstractAsexual organisms often occupy larger and more northern distribution areas than their sexual relatives, and tend to colonize more frequently previously glaciated areas. These phenomena, summarized under the term "geographical partheno ‐ genesis", seem to imply a short‐term advantage of asexual reproduction. Alpine biota, for instance, with their short growing seasons, cold climates and climatic histories shaped by glaciations are predisposed for the evolution and spread of apomictic plants. However, patterns and causes of geographical parthenogenesis for alpine species remain elusive, and for many alpine taxa the mode of reproduction is only poorly characterized. A survey of apomictic species in the European Alps presents some examples and case studies on geographical parthenogenesis. The distribution pattern may be explained by better colonizing abilities of asexual organisms because of uniparental reproduction. Apomixis has been advantageous for re‐colonization of the Alps after the retreat of glaciers, because of their ability to rapidly found populations via single individuals (Baker's Law). Asexual organisms also may perform better in diverse and narrow ecological niches. The distributional superiority of asexuals has also been attributed to indirect advantages of hybridity and/or polyploidy. Sexual hybrids or polyploids, however, when compared to sexual diploid progenitors, do not show patterns of geographical parthenogenesis. However, in the Alps, climatic oscillations may have triggered range fluctuations of species and breakdown of crossing barriers. Interspecific hybridization and polyploidy may have spurred recurrent origins of asexuality, while decreasing the fitness of sexual progenitor species. Biogeographical history in combination with the intrinsic advantages of apomixis may explain best the relative success of alpine apomictic plants.