Molecular relationships of the bear cuscus, Ailurops ursinus (Marsupialia: Phalangeridae)

Abstract

DNA-hybridisation experiments, involving seven species of Phalangeridae and two outgroup taxa in a complete 9 x 9 matrix, unequivocally placed the bear cuscus, Ailurops ursinus, nearest to the Phalangerini (Phalanger and Spilocuscus), with Trichosurini (Trichosurus) sister to both; and confirmed earlier molecular studies indicating that the ground cuscus, Strigocuscus gymnotis, is not a trichosurin but is closest to Phalanger. Our results thus conflict with the most thorough cladistic-anatomical study of phalangerids, which placed the bear cuscus outside all other Phalangeridae as the sole living member of Subfamily Ailuropinae; instead, we suggest that Ailurops should be considered representative of a tribe of Phalangerinae, Ailuropini, while Trichosurus (and presumably Wyulda, which was not examined here, as well as fossil Strigocuscus) would be removed from Phalangerinae and be considered a second subfamily of Phalangeridae, Trichosurinae, limited to Australia. Our estimate of the time of divergence of Ailurops and other phalangerines is about 16 myrbp; of Trichosurinae and Phalangerinae, about 21 myrbp. Thus, a single Early Miocene vicariant event between Australia and Papua New Guinea, which isolated phalangerines in the latter region, followed by dispersal of the included ailuropins to (or vicariant separation on) Sulawesi, would be sufficient to account for family-level cladogenesis in Phalangeridae.