Historical biogeography and phylogeny of Typhlatya cave shrimps (Decapoda: Atyidae) based on mitochondrial and nuclear data

Aim Our aim was to produce a dated phylogeny of Typhlatya, a stygobiont shrimp genus with an extremely disjunct localized distribution across the Mediterranean, the central Atlantic and eastern Pacific. Using phylogenetic analyses, we examine the role of dispersal and plate tectonics in determining its distribution. Location Western Mediterranean, Ascension Island, Bermuda, Bahamas, Yucatan, Caribbean, Galapagos, Western Australia. Methods Thirteen of the 17 species of Typhlatya were analysed, using Stygiocaris, Halocaridina and Antecaridina as outgroups. Fragments of three mitochondrial and three nuclear genes were combined into a data set of 2449 mitochondrial and 1374 nuclear base pairs. Results Phylogenetic trees clearly showed Typhlatya to be paraphyletic, with the Galapagos species clustering with Antecaridina. Only the phylogenetic position of Typhlatya monae (Hispaniola and Puerto Rico) showed some uncertainty, appearing as the sister group to the Australian genus Stygiocaris on the most likely topology. We estimated an average age of 45Myr (30.661.1Myr) for the most recent common ancestor of Typhlatya + Stygiocaris + Antecaridina + Halocaridina. All Typhlatya (except Typhlatya galapagensis) + Stygiocaris derived from a node dated to 35.7Ma (25.747.0Ma), whereas the ancestor of all Typhlatya species (excluding T. monae and T. galapagensis) lived 30.7Ma (21.940.4Ma). Main conclusions Typhlatya is paraphyletic and apparently absent from the eastern Pacific, with T. galapagensis clustering with Antecaridina. The remaining Typhlatya species form a robust monophyletic group with Stygiocaris, and both molecular and morphological evidence support the recognition of three sublineages: (1) Typhlatya s. str., AtlanticMediterranean, embracing all Typhlatya species minus T. monae; (2) Stygiocaris, limited to north-western Australia; and (3) T. monae (Caribbean), for which a new genus could be erected. No congruence was found between temporal and geographical projections of cladogenetic events within Typhlatya/Stygiocaris and the major plate tectonic events underlying Tethyan history.