Molecular phylogeny and historical biogeography of marine palaemonid shrimps (Palaemonidae: Palaemonella–Cuapetes group)

Palaemonidae is the most speciose shrimp family within the infraorder Caridea composed predominately of freshwater or marine symbiotic species. The subject of this study is a group of mainly free-living marine taxa representing a specific lineage basally separated from most of the symbiotic marine palaemonid genera. Phylogenetic and biogeographic relationships were explored by analysing sequence data from two mitochondrial and four nuclear markers. Maximum likelihood and Bayesian analyses, based on sequences from 52 species of 11 genera, provided similar tree topologies revealing the genera Palaemonella, Cuapetes and Eupontonia as non-monophyletic groups. Divergence time and S-DIVA analyses pointed out that the present study group originated during the Late Cretaceous in the Paleotethys region respective to the present Indo-West Pacific area, a minor part of which spread out to the eastern Pacific during the Paleocene, followed by further migration into the Atlantic (before the closure of the Panama Isthmus). The ancestral state reconstruction of host associations revealed eight independent evolution lineages originating from free-living ancestors, thus entering the primary symbioses. The first associations with Cnidaria are estimated at the Eocene. This study points on a need in taxonomic revisions of the aphyletic genera.