Taxonomy, phylogeny, historical biogeography, and historical ecology of the genus Pontonia (Crustacea: Decapoda: Caridea: Palaemonidae)

Species of the genus Pontonia Latreille, 1829, are distributed in tropical and subtropical waters around the world, living in association with either molluscan or ascidian hosts. In the present taxonomic revision, Pontonia sensu lato is divided into six genera: Pontonia sensu stricto; Ascidonia gen. nov., Rostronia gen. nov., Dactylonia gen. nov., Odontonia gen. nov., and Bruceonia gen. nov. A total of 29 species is described and figured, four of which are new to science: Pontonia pilosa spec. nov., Dactylonia holthuisi spec. nov., Odontonia rufopunctata spec. nov., and O. seychellensis spec. nov. The division in six genera is based on a stepwise phylogenetic analysis using morphological characters, performed using PAUP and McClade software. The hypothesized phylogeny is used to analyse the historical biogeography of the shrimps. A deductive method using Brooks Parsimony Analysis (BPA) is performed with regards to the Atlantic and East Pacific areas. The distribution patterns in the Indo-West Pacific are tested against the three scenario’s explaining the ‘East Indies Triangle of maximum diversity’. The historical ecology of the shrimps is analysed using their hypothesized phylogeny. In analogy with the historical biogeographical analyais, a deductive BPA method was applied, measuring the fit of the shrimp phylogeny on the hypothesized host phylogeny at different taxonomical levels of the hosts.