Phylogeny and historical biogeography of the cave-adapted shrimp genus Typhlatya (Atyidae) in the Caribbean Sea and western Atlantic
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AbstractAim To infer phylogenetic relationships among five species of the caveadapted shrimp genus Typhlatya in order to test competing hypotheses of dispersal and colonization of the disjunct cave localities occupied by these five species.LocationTyphlatya species are found in caves and anchialine ponds across the northern margin of the Caribbean Sea, along the Mediterranean and Adriatic coasts and on oceanic islands in the Atlantic and eastern Pacific oceans. This study focuses on five species, one from Bermuda, one from the Caicos Islands and three from the Yucatan Peninsula of Mexico.Methods Partial sequences (c. 1400bp) from the mitochondrial cytochrome b, 16S rDNA and COI genes were obtained from representative samples of the five species. Phylogenetic inference was carried out with maximum parsimony and maximum likelihood analyses. Parsimony networks were constructed for the Bermudian species Typhlatya iliffei and one Yucatan species Typhlatya mitchelli, to determine the degree of connectivity among populations inhabiting different cave systems.Results All three land masses were recovered as monophyletic. The two insular marine species from Bermuda and the Caicos Islands formed a clade, while the three continental freshwater species from the Yucatan Peninsula formed another. Within both Bermuda and the Yucatan, shared haplotypes were found in different cave systems, suggesting recent or ongoing gene flow among populations in both locales.Main conclusions The two insular marine Typhlatya species originated from an ancestral marine population, possibly already caveadapted, that is suggested to have colonized the Caicos Islands and subsequently dispersed to Bermuda via the Gulf Stream. Divergence estimates suggest that colonization occurred before the formation of presentday anchialine cave habitat, which did not form on either island until the late Pliocene to early Pleistocene. Divergence estimates also indicate that the Yucatan freshwater species split before the formation of freshwater cave habitat in the Yucatan. These species could have inhabited crevicular marine habitats before the late Pliocene/early Pleistocene in the Yucatan or elsewhere in the Caribbean, and subsequently migrated to freshwater caves once they formed.
