Abstract
The subterranean niche harbours animals with extreme adaptations. These adaptations decrease the vagility of taxa and, along with other behavioural adaptations, often result in isolated populations characterized by small effective population sizes, high inbreeding, population bottlenecks, genetic drift and consequently, high spatial genetic structure. Although information is available for some species, estimates of genetic diversity and whether this variation is spatially structured, is lacking for the Cape mole-rat (Georychus capensis). By adopting a range-wide sampling regime and employing two variable mitochondrial markers (cytochrome b and control region), we report on the effects that life-history, population demography and geographic barriers had in shaping genetic variation and population genetic patterns in G. capensis. We also compare our results to information available for the sister taxon of the study species, Bathyergus suillus. Our results show that Georychus capensis exhibits low genetic diversity relative to the concomitantly distributed B. suillus, most likely due to differences in habitat specificity, habitat fragmentation and historical population declines. In addition, the isolated nature of G. capensis populations and low levels of population connectivity has led to small effective population sizes and genetic differentiation, possibly aided by genetic drift. Not surprisingly therefore, G. capensis exhibits pronounced spatial structure across its range in South Africa. Along with geographic distance and demography, other factors shaping the genetic structure of G. capensis include the historical and contemporary impacts of mountains, rivers, sea-level fluctuations and elevation. Given the isolation and differentiation among G. capensis populations, the monotypic genus Georychus may represent a species complex.
Highlights
The life history of a species along with its habitat specificity, habitat matrix and the spatial and temporal variation in geological and climatic factors through evolutionary time, shape genetic patterns and drives diversification and speciation (e.g., [1, 2, 3, 4])
We investigate the effects of life-history characteristics on shaping genetic variation and spatial genetic patterns in G. capensis
Georychus capensis is a subterranean species, which exhibits low genetic diversity relative to its concomitantly distributed sister genus, Bathyergus. This species shows strict adherence to certain ecological variables [19]; the spatial heterogeneity in the distribution of such suitable habitat results in geographically discrete and isolated populations. Because of these considerations, the extreme isolation of G. capensis populations leads to local population declines and low effective population sizes—inbreeding and bottlenecks may reduce genetic diversity
Summary
The life history of a species along with its habitat specificity, habitat matrix and the spatial and temporal variation in geological and climatic factors through evolutionary time, shape genetic patterns and drives diversification and speciation (e.g., [1, 2, 3, 4]). Populations of fossorial species regularly exhibit a localized and patchy distribution adhering to specific soil types [5, 7, 9, 10, 15, 16, 17, 18, 19] with restricted gene-flow between them [4, 9, 17] Given such spatial isolation and often small effective population sizes, fossorial animals are prone to inbreeding and typically experience bottlenecks and genetic drift, which in turn leads to low genetic diversity and rapid divergences between isolated populations [4, 5, 7, 9, 10, 11, 12, 17, 20, 21, 22, 23, 24]
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