Rafting spiders or drifting islands? Origins and diversification of the endemic trap‐door spiders from the Balearic Islands, Western Mediterranean

Abstract

AbstractAimTo unravel the origins and to infer the processes of diversification in the low‐vagility nemesiid trap‐door spiders of the Balearic Islands. The specific goals were: (1) to determine whether nemesiid spiders colonized the islands by oversea dispersal, or whether they are the result of the fragmentation of a once continuous distribution by continental drift, and (2) to test whether the Balearic lineages have undergone local diversification processes.LocationsBalearic Islands, Iberian Peninsula, Western Mediterranean.MethodsMultilocus molecular phylogenetic inference using parsimony and model‐based methods, and divergence time estimation with relaxed clocks and informed substitution rate priors, and biogeographical ancestral reconstruction inferred in a Bayesian framework.ResultsPhylogenetic analyses revealed the monophyly of the genera Iberesia and Nemesia. Four independent clades were recovered for the Balearic fauna. One of the clades included a formerly unknown species from Minorca. The Balearic clades split from their continental relatives in the early Tortonian, except for Iberesia brauni, which dates to the Messinian‐Zanclean. The biogeographical reconstruction indicated that the Balearic fauna probably originated in the Betic region of the Iberian Peninsula.Main conclusionsThe presence of Nemesia on the Balearic Islands was explained by fragmentation of an ancestral distribution range that included the Betic region and the islands in the Early Tortonian. The arrival of Iberesia to the islands, however, was the result of a secondary range expansion that was facilitated by the emergence of land bridges with the continent during the Messinian salinity crisis (MSC). Similarly, the drops in the sea level that occurred during the MSC and subsequently in the Quaternary glacial cycles established land passages between Majorca and Minorca.