The non-dereliction in evolution: Trophic specialisation drives convergence in the radiation of red devil spiders (Araneae: Dysderidae) in the Canary Islands

Natural selection plays a key role in deterministic evolution, as clearly
illustrated by adaptive radiations. Unlike most spiders, Dysdera species
display a high variability of cheliceral morphologies, which has been
suggested to reflect different levels of specialisation to feed on
isopods. In this study, we integrate geometric morphometrics and
experimental trials with a fully resolved phylogeny of the highly diverse
endemic species from the Canary Islands to (1) characterize cheliceral
morphologies, (2) unravel their dietary function, (3) examine if they
evolved multiple times independently (4) verify whether convergent
evolution of morphotypes has occurred and (5) test if specialization could
lead to evolutionary irreversibility. We show the existence of nine
cheliceral morphotypes and uncovered their significance for trophic
ecology. Further, we demonstrate that similar ecomorphs evolved multiple
times in the archipelago, providing a novel study system to explain how
convergent evolution and irreversibility due to specialization may be
combined to shape phenotypic diversification in adaptive radiations.