Hydromyini is a very large, diversetribe ofmuroidrodents in the subfamilyMurinae. They are the dominant native rodents inAustralasia and one of only two native rodent groups there, the other being theR. fuscipes group of the genusRattus in the tribeRattini.[1] They are also found in parts ofSoutheast Asia.
They are thought to be relatively early offshoots from the Murinae, with onlyRattini andPhloeomyini being morebasal than them. They likely colonizedNew Guinea (then a part ofSahul) from either theSunda Shelf or thePhilippines during the lateMiocene or earlyPliocene, about 5 million years ago, and diversified extremely rapidly. From here, they colonized Australia about 2-3 million years ago, undergoing majoradaptive 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 theMurinae, 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 thesemiaquatictype genusHydromys, which translates directly to "water mouse", only a few members of the tribe such asHydromys andXeromys are semiaquatic; the majority are terrestrial, and some such asNotomys are even specifically adapted to arid environments.
InAustralia, many members of this tribe have gone extinct very rapidly since the 19th century due to introduced predators and habitat alteration (such as development andfire suppression). Prominent examples include thewhite-footed rabbit rat (Conilurus albipes),lesser stick-nest rat (Leporillus apicalis),blue-grey mouse (Pseudomys glaucus) and over half the recent species in the genusNotomys, 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, theBramble Cay melomys (Melomys rubicola), which went extinct in the early 2010s, was the first recorded extinction of an animal due tosea level rise.[7]
