Séminaire Ecobio : Miquel Arnedo

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Endless species, yet limited forms: Diversification of red devil spiders in the Macaronesia

 

Adaptive radiations on islands have fascinated evolutionary biologist for decades. Because of
their quasi-experimental condition, oceanic archipelagos have been a testing ground for
understanding the origins of species and identifying the drivers of diversification. Here, we
document one of the most spectacular cases of species proliferation and diversification of
spiders on islands. The ground dweller genus Dysdera, the red devil spiders, includes
approximately 300 species of mostly Western Palearctic distribution. They have colonized the
northeaster Atlantic Macaronesia Archipelagos multiple times independently and undergone
local diversification on some of them. To date, approximately 60 endemic species have been
described from the Canary Islands. Unlike other highly diverse endemic lineages, Dysdera
colonised early during the geological history of the archipelago and can be considered a Tertiary
relict. The integration of morphological and molecular data unveiled limited evidence of
introgression, yet multiple cases of deep phylogeographic structure, suggesting a mostly
allopatric speciation process. On the other hand, Dysdera displays a great variability in the size
and shape of its mouthparts, which is unique among spiders. Multiple types of mouthparts have
evolved convergently in the Canary Islands. The different types are associate with increasing
levels of feeding specialisation, specifically on terrestrial isopods, which may explain in part
the remarkable high levels of species coexistence in the archipelagos.