MITOCHONDRIAL-DNA EVOLUTION OF TETRAPLOIDS IN THE GENUS NEOBATRACHUS (ANURA, MYOBATRACHIDAE)

The Australian burrowing frog-genus Neobatrachus currently contains si x diploid and four tetraploid species that are recognized by a combina tion of morphological, cytogenetic, and behavioral characters. Sequenc es of the mitochondrially encoded cytochrome oxidase I (COI) gene were used to reconstruct historical relationships among diploid and tetrap loid species, Data were anal)zed by using parsimony, minimum evolution , and maximum likelihood as optimality criteria. Based on our results, we hypothesize that there have been at least two origins of tetraploi ds: one gave rise to an ''eastern'' lineage (N. sudelli from Queenslan d and South Australia, N. centralis from South Australia and Western A ustralia, and N. aquilonius from the Northern Territory); the other ga ve rise to a ''western'' lineage (N. kunapalari and N. aquilonius from Western Australia). Origins of the eastern lineage from extant diploi ds were not resolved. Members of the western lineage may be derived fr om N. albipes or N. fulvus. We conclude that tetraploid lineages may b e older than previously suggested, that there have been multiple origi ns of tetraploidy in Neobatrachus, and that some of the tetraploids ma y have speciated subsequent to their origin. Our results suggest a pre liminary framework in which to address further questions on the origin s of tetraploids and their subsequent patterns of speciation.