Electrophoretic delineation of species boundaries within the short-necked freshwater turtles of Australia (Testudines: Ghelidae)

A total of 222 specimens from 55 populations of short-necked chelid turtle was collected from drainages in Australia and Papua New Guinea. Two populations were initially considered to belong to different diagnosable taxa if all individuals in one population could be distinguished from all individuals in the other by fixed allozyme differences. When two populations or diagnosable taxa shared allozymes at all presumptive loci, their profiles were combined into a single diagnosable taxon. Comparisons between populations and emerging diagnosable taxa were repeated until no further changes were possible. The species Elseya dentata comprised five clearly diagnosable taxa, differing by between 4 and 19 fixed allozyme differences. The currently recognized El. latisternum and El. novaeguineae were each a single diagnosable taxon, and there were three diagnosable taxa, including a sibling pair, that could not be assigned to a currendy described Elseya species. In contrast, all forms of Emydura were very closely related, with no two taxa differing by more than three fixed allozyme differences. There were three diagnosable taxa in the north (Em. victoriae, Em. subglobosa and one new form), though support for them was marginal. In the south, Em. macquarii, Em. krefflii and Em. signata formed only a single diagnosable taxon, even sharing rare alleles. If the phylogenetic species concept is adopted, there is support for recognition of 16 species of short-necked turtle in Australia, including Pseudemydura umbrina. Currendy only 10 are described. Our data also provide evidence of reproductive isolation in some cases (sympatric or parapatric), and comparative evidence (sensu Mayr) in others, than the traditional biological species concept applies also to these diagnosable taxa.