Phylogeography of the pademelons (Marsupialia: Macropodidae: Thylogale) in New Guinea reflects both geological and climatic events during the Plio-Pleistocene

Abstract

Aim: Alternative hypotheses concerning genetic structuring of the widespread endemic New Guinean forest pademelons (Thylogale) based on current taxonomy and zoogeography (northern, southern and montane species groupings) and preliminary genetic findings (western and eastern regional groupings) are investigated using mitochondrial sequence data. We examine the relationship between the observed phylogeographical structure and known or inferred geological and historical environmental change during the late Tertiary and Quaternary. Location: New Guinea and associated islands. Methods: We used primarily museum specimen collections to sample representatives from Thylogale populations across New Guinea and three associated islands. Mitochondrial cytochrome b and control region sequence data were used to construct phylogenies and estimate the timing of population divergence. Results: Phylogenetic analyses indicated subdivision of pademelons into ‘eastern’ and ‘western’ regional clades. This was largely due to the genetic distinctiveness of north-eastern and eastern peninsula populations, as the ‘western’ clade included samples from the northern, southern and central regions of New Guinea. Two tested island groups were closely related to populations north of the Central Cordillera; low genetic differentiation of pademelon populations between north-eastern New Guinea and islands of the Bismarck Archipelago is consistent with late Pleistocene human-mediated translocations, while the Aru Islands population showed divergence consistent with cessation of gene flow in the mid Pleistocene. There was relatively limited genetic divergence between currently geographically isolated populations in subalpine and nearby mid-montane or lowland regions. Main conclusions: Phylogeographical structuring does not conform to zoogeographical expectations of a north/south division across the cordillera, nor to current species designations, for this generalist forest species complex. Instead, the observed genetic structuring of Thylogale populations has probably been influenced by geological changes and Pleistocene climatic changes, in particular the recent uplift of the north-eastern Huon Peninsula and the lowering of tree lines during glacial periods. Low sea levels during glacial maxima also allowed gene flow between the continental Aru Island group and New Guinea. More work is needed, particularly multi-taxon comparative studies, to further develop and test phylogeographical hypotheses in New Guinea.