Phylogeny of the rock wallabies, Petrogale (Marsupialia: MMMMacropodidae). Part II: Detection of hybridisation among macropodines

Phylogenetic relationships among rock-wallabies, Petrogale (Marsupialia: Macropodidae), have proven difficult to resolve. Given the documented interspecific hybridisation in the wild and the ease with which hybrids can be bred in captivity, introgression and hybrid speciation are likely explanations for these difficulties. In this paper, an attempt is made at using a phylogenetic approach to identify Petrogale hybrids of known origin. The Hybrid Detection Criterion (HDC) test is applied to DNADNA hybridisation data for 15 full species, two natural yard-bred hybrids, and two artificial hybrids from the same pairs of parental species. While the yard-bred hybrids elude detection with this technique, the artificial hybrids, consisting of equimolar mixture of parental extracts, are easily identified. Moreover, splitsgraphs constructed from five pairs of natural and artificial hybrids, including those evaluated with HDC, and their parents show that, in all cases but one, these two kinds of hybrids do not group together. Because the HDC assumes an intermediate phylogenetic position of the hybrid between its postulated parents, it is likely that unequal crossing-over, or another recombination event, affects the results of the test. These conclusions cast some doubt on the possibility of accurately detecting Petrogale hybrids with a phylogenetic approach.