Geographical Parthenogenesis in Alpine and Arctic Plants

Abstract

The term “Geographical parthenogenesis” describes the phenomenon that asexual organisms usually occupy larger and more northern distribution areas than their sexual relatives, and tend to colonize previously glaciated areas. Several case studies on alpine and arctic plants confirm the geographical pattern, but the causal factors behind the phenomenon are still unclear. Research of the last decade in several plant families has shed light on the question and evaluated some of the classical evolutionary theories. Results confirmed, in general, that the advantages of uniparental reproduction enable apomictic plants to re-colonize faster in larger and more northern distribution areas. Associated factors like polyploidy seem to contribute mainly to the spatial separation of sexual and asexual cytotypes. Ecological studies suggest a better tolerance of apomicts to colder climates and temperate extremes, whereby epigenetic flexibility and phenotypic plasticity play an important role in occupying ecological niches under harsh conditions. Genotypic diversity appears to be of lesser importance for the distributional success of asexual plants. Classical evolutionary theories like a reduced pressure of biotic interactions in colder climates and hence an advantage to asexuals (Red Queen hypothesis) did not gain support from studies on plants. However, it is also still enigmatic why sexual outcrossing remains the predominant mode of reproduction also in alpine floras. Constraints for the origin of apomixis might play a role. Interestingly, some studies suggest an association of sexuality with abiotic stresses. Light stress in high elevations might explain why most alpine plants retain sexual reproduction despite other environmental factors that would favor apomixis. Directions for future research will be given.

Geometric Morphometric Versus Genomic Patterns in a Large Polyploid Plant Species Complex

“…Moreover, the UMAP analysis of ecological similarity among sexuals and apomicts inferred substantial ecological shifts of the apomicts far outside the range of the progenitor species ( Figure S13 ). Ecological niche shifts can contribute significantly to the range expansions of allopolyploid apomicts compared to their progenitors (“geographical parthenogenesis”) [ 9 , 24 , 186 ]. We also observed allopolyploids with intermediate ecology but transgressive morphology, i.e., with characters outside the parental’s morphospace (e.g., R. × hungaricus and R. × leptomeris).…”

Distinct geographic parthenogenesis in spite of niche conservatism and a single ploidy level: A case of Rubus ser. Glandulosi (Rosaceae)

“…One of the often emphasised potential drivers of GP is the advantage of uniparental reproduction of asexuals for colonisation (Tilquin & Kokko, 2016). Its effect is stronger in autonomous than in pseudogamous apomicts, and probably stronger in the case of self‐sterility of sexual relatives (Hörandl, 2023). However, R .…”

“…Glandulosi , its drivers are likely system‐specific. It is generally presumed that apomicts are repeatedly derived from sexuals (Hörandl, 2023). If this presumption is valid on a recent evolutionary scale, it must inevitably result in higher genotypic diversity of apomicts that are sym‐ or parapatric with sexuals compared with the allopatric ones.…”

Apomixis goes a long way: Genetic evidence of persistence and long‐distance seed dispersal in an ancient landscape

“…Brock, 2004;Rambuda & Johnson, 2004). Much needed molecular studies at regional scales to understand the evolutionary and biogeographical history of apomictic species are emerging in recent years but are mainly limited to temperate zones in the Northern Hemisphere (Coughlan et al, 2017;Hörandl, 2023;Karbstein et al, 2021), while studies in more ancient, unglaciated landscapes are still lacking.…”

“…Brock, 2004; Rambuda & Johnson, 2004). Much needed molecular studies at regional scales to understand the evolutionary and biogeographical history of apomictic species are emerging in recent years but are mainly limited to temperate zones in the Northern Hemisphere (Coughlan et al., 2017; Hörandl, 2023; Karbstein et al., 2021), while studies in more ancient, unglaciated landscapes are still lacking. Molecular data can be useful for confirmation of apomixis, assessing the relative contributions of sexual and asexual reproduction, and understanding the genetic diversity and phylogeographical dynamics of apomictic species.…”