Chromosome Evolution, Phylogeny and Speciation of Rock Wallabies (Petrogale, Macropodidae)

Abstract

Twenty-one taxa of rock wallabies presently grouped in 11 species were studied at their type localities and elsewhere. All were chromosomally distinct except for Petrogale xanthopus and P. x. celeris, and all taxa appear to have evolved from an ancestor with a karyotype like that of Thylogale billardierii. The chromosomal structural rearrangements that distinguish the karyotypes of the various taxa of rock wallabies from that of T. billardierii provided a set of derived characters from which a phylogenetic arrangement has been constructed. Chromosome rearrangements that apparently contribute to reproductive isolation were found at hybrid zones between taxa of parapatric distribution. The reproductive capacity of laboratory bred hybrids was assessed in relation to their chromosomal heterozygosity. It is concluded that reproductive isolation in parapatry was sometimes increased by the establishment of different chromosome fusions involving one ancestral chromosome common to both parapatric taxa.