American Society of Ichthyologists and Herpetologists, Portland, OR, July 2009.

Phylogeny and Species Boundaries Within the Catfish Family Plotosidae.

Unmack, Adams, Hardy, Hartley, Allen, and Johnson.

Plotosid catfishes are unusual within Siluriformes in that they are only one of two families with marine representatives. As currently defined the family has 9 genera and ~40 species. Five of those genera are restricted to freshwaters in Australia and New Guinea, while the remaining four genera are marine. Of the marine genera, all but one is by and large restricted to seas around Australia and New Guinea. The last marine genus, Plotosus is extremely widespread, occurring from South Africa to Japan to Australia. We reconstructed phylogenetic relationships within the family based on nearly all freshwater species and all of the genera except Euristhmus which was unavailable to us. We sequenced ~5,700 bp from mitochondrial DNA plus two nuclear genes, 18S (~1800 bp) and RAG1 (~1000 bp). Results suggest that the family was originally marine, with an invasion into freshwaters. Most genera were resolved as monophyletic, except for one species in Porochilus which came out within Neosilurus, one species of Tandanus formed an independent lineage and the genus Plotosus was not clearly resolved. We had broad geographic coverage of Australian freshwater species to assess species boundaries using allozyme electrophoresis and the cytochrome b gene. The most widespread species, Neosilurus hyrtlii appears to consist of as many as four species, while N. pseudospinosus maybe separated into two species. We also support the previous recognition of two undescribed species in the genus Tandanus. The remaining species all showed levels of variation consistent with their current designations.