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Exploring the role of within-island ecogeographical factors: insights from the genetic diversity of Cretan trap-door spiders (Cyrtocarenum cunicularium, Ctenizidae, Araneae)
Crete (Aegean Sea, Greece), as other Mediterranean islands, has a complex paleogeographical history, including several cycles of fragmentation into paleoislands and subsequent reconnection. Here, we use the Cretan trap-door spider Cyrtocarenum cunicularium as a model organism to explore the importance of within-island evolutionary processes, such as paleogeographic events and climatic changes. We assessed the phylogeny, population clustering and historical demography of 61 specimens with mitochondrial (COI) and nuclear (H3) markers. We investigated the isolation-by-distance (IBD) and spatial diffusion processes that have shaped their past and current distribution and estimated the effect of niche divergence, using species distribution modeling (SDM). Two genetic lineages have continuously been distributed in the west and east part of Crete during the last 2 Mya. Their genetic structure is concordant with Crete’s fragmentation into paleoislands during the Pliocene and additionally affected by the sea-level oscillations and climatic changes due to the Pleistocenic glacial cycles. In central Crete, some evidence of genetic admixture between them was found, which needs to be further explored. According to SDM, the niche of each lineage corresponds to different environmental parameters, while IBD was also detected. The divergence between the “West” and “East” lineages was promoted by paleogeographical factors but seems to be maintained by the species’ poor dispersal abilities and the local ecological adaptation of each lineage. The case of the Cretan C. cunicularium highlights the combining effect of ecogeographical and behavioral factors in shaping insular biodiversity.
IS16082 Accepted 15 April 2017
© CSIRO 2017