Phylogenetic relationships of new world needlefishes (Teleostei : Belonidae) and the biogeography of transitions between marine and freshwater habitats

The New World clade of needlefishes (Belonidae) includes species distribute d along the Pacific and Atlantic coasts of the Americas and in freshwater b asins of Central and South America. Phylogenetic relationships among 13 spe cies of the group were assessed based on data from two nuclear genes (RAG2 and Tmo-4C4), two mitochondrial genes (cytochrome b and 16S rRNA), and a sm all suite of morphological characters. In general, there was concordance be tween separate analyses of nuclear and mitochondrial characters, and RAG2 w as found to be a particularly useful gene for phylogeny reconstruction. Mor phology supported an alternative phylogenetic pattern, but this was probabl y a result of the small number of characters and the lack of a thorough ana tomical survey, The total evidence hypothesis divides the group into two ma jor clades, In one, Pseudotylosurus from freshwater in South America is mos t closely related to a pair of Strongylura species from the western and eas tern Atlantic; in the other, Potamorrhaphis and Belonion from South America n freshwater are related to a clade of Strongylura from marine and freshwat er habitats of the eastern Pacific and western Atlantic. Optimization of ha bitat on the total evidence tree, combined with paleogeographic data, sugge sts that four independent entries into freshwater have taken place-one in C entral America, and three in South America.