Integrative taxonomy and evolutionary history of a newly revealed spider Dysdera ninnii complex (Araneae: Dysderidae)

The spider genus Dysdera is a species-rich clade of specialized woodlice predators, composed typically of complexes of sibling species. Here, we analyse the Dysdera ninnii complex, distinguishing three species that exhibit slight but constant differences in the morphology of their copulatory organs, and in their genetic background. We designate a neotype for D. ninnii and redescribe it. We consider Dysdera paves ii Thorell, 1873 to be a junior synonym of Dysdera ninnii Canestrini, 1868. In addition, we describe two new species (Dysdera moravica sp. nov. and Dysdera rnicrodonta sp. nov.). All three species occur in the region of north-eastern Italy, Slovenia, and northwestern Croatia. Dysdera moravica sp. nov. expanded to central Europe. The species occur allopatrically or parapatrically. All three species possess the same diploid number and XO sex chromosome determination. In some individuals we found chromosome fusions, and such polymorphism is common in spiders with holokinetic chromosomes. The analysis of mitochondrial (cytochrome c oxidase subunit I, COI) and nuclear ribosomal (internal transcribed spacer 2, ITS2) DNA markers revealed two clades, one formed by D. ninnii and D. microdonta sp. nov., and a second by D. moravica sp. nov. Species of the first clade are not well defined by DNA markers. We noticed only weak separation of maternally inherited CO/, and even overlap of autosomally inherited ITS2 sequences. We suggest that either short speciation time, unfinished lineage sorting, or rare hybridization events caused this pattern. In one sample of D. microdonta sp. nov. we detected the coxA gene of a Rickettsia species, which is the first record of this parasitic bacteria from the spider family Dysderidae. Dysdera microdonta sp. nov. occurs at higher altitudes than D. ninnii, and their distribution ranges form a long contact zone. Remarkably, we did not record any overlap of the two distribution ranges, suggesting that the lack of a precopulatory interspecific barrier causes a loss of reproduction potential. We hypothesize that because of the unsolved interspecific barrier together with only tiny differences in morphology and CO/ sequences, and no differences in karyotypes and ITS2 sequences, the D. ninnii species complex is evolutionarily young.