Oryzomys Gorgasi - Taxonomy

Taxonomy

Oryzomys gorgasi was first found in Antioquia Department of northwestern Colombia in 1967 during an expedition by the U.S. Army Medical Department and the Gorgas Memorial Laboratory. In 1971, Field Museum zoologist Philip Hershkovitz described a new species, Oryzomys gorgasi, on the basis of the single known specimen, an old male. He named the animal after physician William Crawford Gorgas, the namesake of the Gorgas Memorial Laboratory. Hershkovitz considered the new species most closely related to Oryzomys palustris, which at the time included North and Central American populations now divided into several species, including the marsh rice rat (O. palustris) and O. couesi. The species was not recorded again until 2001, when Venezuelan zoologist J. Sánchez H. and coworkers reported on 11 specimens collected in coastal northwestern Venezuela in 1992, 700 km (400 mi) from the Colombian locality. They confirmed that O. gorgasi is a distinct species related to the O. palustris group.

In 2001, Donald McFarlane and Adolphe Debrot described a new Oryzomys species from the Dutch island of Curaçao off northwestern Venezuela. For their description, they used subfossil material from owl pellets, including two partial skulls and several hemimandibles. They referred the species to Oecomys, a group of arboreal (tree-living), mainly South American rodents related to Oryzomys. O. curasoae has also been known as the "Curaçao Rice Rat" and the "Curaçao Oryzomys".

Marcelo Weksler and colleagues removed most of the species then placed in Oryzomys from the genus in 2006, retaining only the marsh rice rat and related species, including O. gorgasi. They also kept O. curasoae in the genus and suggested that it may not be distinct from O. gorgasi. In a 2009 paper, R.S. Voss and Weksler examined the two and concluded that they represented the same species on the basis of direct comparisons and a phylogenetic analysis. The resultant tree placed O. curasoae and O. gorgasi sister to each other and closer to O. couesi than to the marsh rice rat. Accordingly, they placed O. curasoae as a junior synonym of the earlier described O. gorgasi.

Oryzomys gorgasi is the southeasternmost representative of the genus Oryzomys, which extends north into the eastern United States (marsh rice rat, O. palustris). O. gorgasi is further part of the O. couesi section, which is centered around the widespread Central American O. couesi and also includes six other species with more limited and peripheral distributions. Many aspects of the systematics of the O. couesi section remain unclear and it is likely that the current classification underestimates the true diversity of the group. Oryzomys is classified in the tribe Oryzomyini, a diverse assemblage of American rodents of over a hundred species, and on higher taxonomic levels in the subfamily Sigmodontinae of family Cricetidae, along with hundreds of other species of mainly small rodents.