Thursday, April 21, 2016

[Mammalogy • 2016] Rattus detentus • A New Species of Rattus (Rodentia: Muridae) from Manus Island, Papua New Guinea

Admiralties Rat | Rattus detentus
 Timm, Weijola, Aplin, Flannery & Pine, 2016

Fig. 1. A) Adult female Rattus detentus (PNGMAG 274363—holotype) from Manus Island. B) Nuts from Canarium indicum (Burseraceae) with gnawing marks most likely made by R. detentusE) Collection site of the R. detentus holotype, a traditional subsistence garden and grove of Metroxylon near Kawaliap Village. F) Elevated view of the forest where R. detentus is found.

We describe a new species of Rattus, from 3 modern specimens collected on Manus Island in the Admiralty Group, Papua New Guinea, between 2002 and 2012. Subfossil specimens of early to late Holocene age from the Pamwak archaeological site on Manus Island are referred to the new species on morphological criteria; these confirm the species as a long-term resident of Manus Island. The new species is distinguished by its combination of large size; short tail; dorsal pelage that is coarse, spiny, and dark, with prominent black guard hairs; and sharply contrasting cream ventral pelage. Based on its overall body form, the species is almost certainly terrestrial. The dentition combines robust incisors with relatively small molars and the cranium displays a distinctive mélange of characters—including an elongate and anteriorly expanded rostrum and a mesopterygoid fossa that is narrow anteriorly and broadens to the rear. Sequence data from the mitochondrial control region and 3 nuclear genes place the new species as a highly divergent member of the Australo–Papuan Rattus radiation, with no identified close relative among sampled taxa. Morphological comparisons are made between the new species and other pertinent species of Rattus from the region, including R. sanila, a species known only from Late Pleistocene fossil to Late Holocene subfossil remains from an archaeological site on New Ireland. The conservation status of the new species is discussed in the light of a recent survey that failed to locate surviving populations in 2 areas of natural forest on Manus Island. Further survey work is urgently needed to identify any surviving populations and to assess the role of potential threats to the species.

Key words: Admiralty Islands, Australo–Papuan Region, biogeography, Bismarck Archipelago, conservation, mitochondrial control region, molecular phylogeny, morphology, nuclear genes, Rattus sanila

Rattus detentus, new species Timm, Weijola, Aplin, Flannery, and Pine
Admiralties Rat
syn: Rattus praetor: Williams 1999:244; not Mus praetor Thomas, 1888.
Rattus mordax: Williams 1999:244; not Mus mordax Thomas, 1904a.

Fig. 1. A) Adult female Rattus detentus (PNGMAG 274363—holotype) from Manus Island. B) Nuts from Canarium indicum (Burseraceae) with gnawing marks most likely made by R. detentus. C) Adult female R. detentus (PNGMAG 274363—holotype), dorsal view. D) Adult female R. detentus (PNGMAG 274363—holotype), ventral view. E) Collection site of the R. detentus holotype, a traditional subsistence garden and grove of Metroxylon near Kawaliap Village. F) Elevated view of the forest where R. detentus is found.

Holotype. Adult female obtained by Valter Weijola on 24 August 2012. Voucher specimen fixed in formalin, preserved in spirit, and registered as PNGMAG 274363 (and AMS M45608) in the National Museum & Art Gallery, Port Moresby, Papua New Guinea (Figs. 1A, 1C, and 1D). Tissue sample preserved in ethanol and registered as ABTC 125036 in the Australian Biological Tissue Collection, South Australian Museum, Adelaide. Extracted skull is in excellent condition, all teeth fully erupted and moderately worn, cranium with advanced fusion of basicranial synchondroses (Fig. 2).

Type locality. Vicinity of a small stream near western end of Kawaliap Village, el. 200 m (2°6′40″S, 147°3′40″E), Manus Island, Admiralty Islands, Manus Province, Papua New Guinea.

Fig. 3. Map of the Bismarck Archipelago, Admiralty Islands (in black), and eastern New Guinea, showing the records of Rattus detentus on Manus and of the apparently extinct R. sanila on New Ireland. All known localities of R. detentus are plotted. The closed star represents the type locality, the open star represents the locality of the 2 paratypes, and “X” represents the Pamwak archaeological site. The closed circle represents the Late Pleistocene–Late Holocene Balof 2 archaeological site on New Ireland, the only known locality for R. sanila. Manus and Los Negros are separated by a very narrow channel (indicated by a gap).

Distribution. Currently known as a living animal from 2 localities on Manus and from subfossil remains from the Pamwak archaeological site (Fig. 3).

Etymology. detentus (Latin for detained), in reference to the isolation of this Melanesian Rattus lineage on Manus Island and to the recent use of the island to detain people seeking political and/or economic asylum in Australia.

Robert M. Timm, Valter Weijola, Ken P. Aplin, Stephen C. Donnellan, Tim F. Flannery, Vicki Thomson and Ronald H. Pine. 2016. A New Species of Rattus (Rodentia: Muridae) from Manus Island, Papua New Guinea.  Journal of Mammalogy. DOI: 10.1093/JMammal/gyw034