High genetic diversity of spider species in a mosaic montane grassland landscape

Gene flow and genetic variation were examined within and among populations of five of the most common spider species in shrublands of the mountainous Golden Gate Highlands National Park (GGHNP), South Africa. These species included three active hunters, Dendryphantes purcelli Peckham & Peckham, 1903 (Salticidae), Pherecydes tuberculatus O.P.-Cambridge, 1883 (Thomisidae) and Philodromus browningi Lawrence, 1952 (Philodromidae), and two web-builders, Neoscona subfusca (C.L. Koch, 1837) (Araneidae) and a Theridion Walckenaer, 1802 species (Theridiidae). A total of 249 spiders (57 D. purcelli, 69 N. subfusca, 34 P. browningi, 56 P. tuberculatus and 33 Theridion sp.) were collected and analysed from six shrubland localities in the park. Analyses of sequence variation of the mitochondrial cytochrome oxidase c subunit I (COI) gene for each species revealed relatively low nucleotide diversity (π < 0.0420) but high genetic diversity (Hd > 0.6500) within populations for all species, except P. tuberculatus. Genetic differentiation was also noted to differ between species, with only P. tuberculatus indicating very large divergence (Fst > 0.2500). These results were reflected by gene flow, with D. purcelli, N. subfusca and the Theridion sp. estimated as experiencing more than one disperser per generation. Overall, highest gene flow was found in the two web-building species, indicating possible high dispersal ability of these spiders in the GGHNP. Additionally, constructed phylogenies indicated possible cryptic speciation occurring in the majority of the investigated species. Our current results indicate that the five investigated spider species were able to maintain gene flow between shrubland populations within the GGHNP to some degree, despite the mountainous landscape. However, further analyses incorporating additional molecular markers are needed to properly determine the extent of genetic diversity and gene flow of these species within the GGHNP.