Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia: Macropodidae). IX. Further G-banding studies of the Petrogale lateralis complex: P. lateralis pearsoni, the West Kimberley race, and a population heterozygous for a centric fusion

G-banded metaphase preparations from cultured fibroblasts were used to examine the karyotypes of Petrogale lateralis pearsoni and the West Kimberley (WK) race of P. lateralis. Petrogale lateralis pearsoni was found to retain the ancestral 2n = 22 Petrogale karyotype, while the WK race (2n = 20) was found to be characterized by a 9–10 centric fusion. This taxon had been reported to have an 8–10 fusion. Karyotypic analysis was also used to identify Petrogale populations in the Erskine Range, Western Australia (W.A.) as the WK race and in the Walter James Range, W.A. as the MacDonnell Ranges (MDR) race of P. lateralis. These findings represent significant range extensions for both taxa. A third P. lateralis population, from the Townsend Ridges, W.A., could not be definitively identified to subspecies or race and appears intermediate between the WK and MDR races. Four animals were examined from this population and all possessed an identical 2n = 21 karyotype characterized by homozygosity for a derived acrocentric chromosome 3 (3a) and heterozygosity for a 9–10 fusion. Rearrangement 3a is typical of the MDR race, while the 9–10 fusion is characteristic of the WK race. The polymorphic Townsend Ridges population could result from the de novo creation of a 9–10 fusion (similar in morphology to the 9–10 fusion of the WK race) or it may represent evidence of hybridization between the MDR race and either the WK race or a currently unknown taxon. Additional data will be required to distinguish between these hypotheses.Key words: rock wallabies, Petrogale, chromosome rearrangements, G-banding.