Colonization and diversification of the spider genus Pholcus Walckenaer, 1805 (Araneae, Pholcidae) in the Macaronesian archipelagos: evidence for long-term occupancy yet rapid recent speciation

Macaronesian archipelagos stand apart from other oceanic islands reputed as laboratories for the study of evolution by their proximity to the mainland, lack of subsidence, and steep ecological gradients. The genus Pholcus Walckenaer, 1805, commonly known as daddy-long-leg spiders, is one of the most speciose arthropod groups in the region, with 25 endemic species. In the present study, we use information from four mitochondrial genes, along with morphological data, to examine the phylogenetic relationships and diversification patterns of the genus in the region. Phylogenetic analyses support monophyly of Macaronesian Pholcus including the Moroccan species Pholcus vachoni and hence a single colonization event in the archipelagos. Madeira colonizers most likely originated from the Canaries, and a back-colonization of the nearby mainland receives further support. Estimated lineage divergence times suggest a long-time presence of Pholcus in the region, but also reveal that most present-day species are the result of recent, and probably rapid, speciation events. Diagnostic characters among Macaronesian Pholcus are confined to structures involved in copulation. Coupled with the extremely high diversification rate, the highest recorded for spiders, these copulatory characters suggest that sexual selection has played a key role in the local diversification of Pholcus in Macaronesia.