Hydromyini


Hydromyini is a very large, diverse tribe of muroid rodents 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. 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 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.
Earlier taxonomists formerly split this group into three subfamilies. Although all were later merged into the Murinae, they were still retained as multiple tribes, 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.
The genus Chiropodomys has been found to be the sister group to this tribe, but it has been debated over whether it belongs in its own tribe or is a basal member of the Hydromyini. The American Society of Mammalogists presently classifies it in Hydromyini.
Although the name "Hydromyini" derives from the semiaquatic type genus Hydromys, 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. 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.

Species

Species in the tribe include:Chiropodomys division

Threats

In Australia, many members of this tribe have gone extinct very rapidly since the 19th century due to introduced predators and habitat alteration. Prominent examples include the white-footed rabbit rat, lesser stick-nest rat, blue-grey mouse 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. Another species, the Bramble Cay melomys, which went extinct in the early 2010s, was the first recorded extinction of an animal due to sea level rise.