Dysdera parthenogenetica sp. nov. (Araneae, Dysderidae): A Unique Case of Parthenogenesis in Spiders

We studied the parthenogenetic lineages of the spider Dysdera hungarica (Araneae: Dysderidae). Based on our data, we consider them to constitute a separate taxon, Dysdera parthenogenetica sp. nov. Morphologically, the new species differs mainly by slightly reduced female copulatory organs. The ovaries contain meiotic cells, suggesting that automictic thelytoky occurs in this species. D. parthenogenetica sp. nov. colonised areas west of the ancestral sexual species D. hungarica, especially the Pannonian region; the distribution areas of these species show minimal overlap. The distribution pattern of D. parthenogenetica sp. nov. suggests that the obligate thelytoky in this species originated through geographic thelytoky. D. parthenogenetica sp. nov. has been found in a significantly larger variety of habitats than D. hungarica, including agroecosystems. Therefore, the parthenogenesis of D. parthenogenetica sp. nov. is associated with the ability to populate even habitats without tree or bush cover, often disturbed, which is unfavourable for other Dysdera species. According to the analysis of selected nuclear (ITS2) and mitochondrial markers (COI), D. parthenogenetica sp. nov. showed low genetic diversity (single COI haplotype and two closely related ITS2 haplotypes) in contrast to the ancestral D. hungarica. By separation of D. parthenogenetica sp. nov., D. hungarica becomes a paraphyletic species. D. hungarica is thus one of the first documented cases of paraspecies among spiders. Although D. parthenogenetica sp. nov. exhibits minimum genetic variation at the analysed molecular markers, it displays considerable karyotype diversity. The transition to parthenogenesis was accompanied by a decrease in diploid number through chromosome fusions. Karyotypes of D. parthenogenetica sp. nov. diverged considerably from those of D. hungarica. Potential hybrids between these species would likely produce gametes with defective genomes. There is also a behavioural barrier between these two taxa. Females of D. parthenogenetica sp. nov. refuse to mate.