Hydromyini is a very large, diverse tribe of muroidrodents in the subfamily Murinae. They are the dominant native rodents in Australasia and one of only two native rodent groups there, the other being the R. fuscipes group of the genus Rattus in the tribe Rattini.[1] They are also found in parts of Southeast Asia.
Taxonomy
They are thought to be relatively early offshoots from the Murinae, with only Rattini and Phloeomyini being more basal than them. They likely colonized New Guinea (then a part of Sahul) from either the Sunda Shelf or the Philippines during the late Miocene or early Pliocene, about 5 million years ago, and diversified extremely rapidly. From here, they colonized Australia about 2-3 million years ago, undergoing major adaptive radiation.[2]
Earlier taxonomists formerly split this group into three subfamilies (Hydromyinae, Pseudomyinae, and an unnamed "Old Papuan group"). Although all were later merged into the Murinae, they were still retained as multiple tribes (Anisomyini, Hydromyini, Uromyini, and Conilurini), with other taxonomists splitting them even further. However, a 2008 study found them to comprise a single group that had undergone a rapid diversification after colonizing Sahul, and thus placed them all into a single tribe, Hydromyini.[2]
Although the name "Hydromyini" derives from the semiaquatictype genusHydromys, which translates directly to "water mouse", only a few members of the tribe such as Hydromys and Xeromys are semiaquatic; the majority are terrestrial, and some such as Notomys are even specifically adapted to arid environments.
Distribution
Their center of diversity is in New Guinea, with a secondary one in Australia, but they also range east to the Solomon Islands and west to Borneo and the Philippines, and, if the genus Chiropodomys is included, as far west as northeast India.[4] Members of this tribe in New Guinea and Australia are referred to as the "Old Endemic rodents", to differentiate them from the native Rattus species from the tribe Rattini, which colonized the regions much more recently.[2]
In Australia, many members of this tribe have gone extinct very rapidly since the 19th century due to introduced predators and habitat alteration (such as development and fire suppression). Prominent examples include the white-footed rabbit rat (Conilurus albipes), lesser stick-nest rat (Leporillus apicalis), blue-grey mouse (Pseudomys glaucus) and over half the recent species in the genus Notomys, most of which likely went extinct during the late 19th or early 20th centuries; many other species have also seen significantly reduced populations or range reductions. Genetic studies indicate that many of these species had relatively high genetic diversity prior to European colonization, indicating that they were not suffering from inbreeding beforehand and that high genetic diversity does not shield species from extinctions.[6] Another species, the Bramble Cay melomys (Melomys rubicola), which went extinct in the early 2010s, was the first recorded extinction of an animal due to sea level rise.[7]
