Karyotypes of South-West Pacific Ranid Frogs (Anura:Ranidae)

Karyotypes of 12 species from five genera of Australian, New Guinean and Solomon Islands ranid frogs are reported and for convenience are compared and contrasted with the 2n = 26, fundamental number (FN) = 52 karyotype of Rana, the typical karyotype of the subfamily Raninae. This karyotype was found in the four species of Rana examined. One species, Ceratobatrachus guentheri, had an increased diploid number of 30, a lower FN of 38, and altered relative lengths and centromere positions of pairs 1-5, and several of the smaller pairs. These changes could have resulted from centric fissions and pericentric rearrangements which produced an increase in the number of telocentric chromosomes. Eight species, Batrachylodes vertebralis, Discodeles bufoniformis, D. guppyi, Platymantis boulengeri, P. myersi, P. neckeri, P. solomonis and P. weberi, had reduced diploid numbers and FN. The means by which reduction in diploid number and FN has occurred in these species is unknown, but may involve centric fissions to produce telocentrics, followed by translocation onto other chromosomes, or a process involving pericentric rearrangements to produce telocentric chromosomes followed by fusion of these products. With the exception of Rana, the level of chromosomal rearrangements in the south-west Pacific ranid frogs that occur on archipelagos is high compared with that observed in the continental lineages of this subfamily.