Akodon spegazzinii, also known as Spegazzini's akodont[4] or Spegazzini's grass mouse,[1] is a rodent in the genus Akodon found in northwestern Argentina. It occurs in grassland and forest at 400 to 3,500 m (1,300 to 11,500 ft) above sea level. After the species was first named in 1897, several other names were given to various populations now included in A. spegazzinii. They are now all recognized as part of a single, widespread and variable species. Akodon spegazzinii is related to Akodon boliviensis and other members of the A. boliviensis species group. It reproduces year-round. Because it is widely distributed and common, Akodon spegazzinii is listed as "least concern" on the IUCN Red List.
Akodon spegazzinii is medium in size for the A. boliviensis species group. The coloration of its upperparts varies considerably, from light to dark and from yellowish to reddish brown. The underparts are yellow-brown to gray. The eyes are surrounded by a ring of yellow fur. The skull contains an hourglass-shaped interorbital region (between the eyes) and various features of the skull distinguish the species from its close allies. Head and body length is 93 to 196 mm (3.7 to 7.7 in) and body mass is 13.0 to 38.0 g (0.46 to 1.34 oz). Its karyotype has 2n = 40 and FN = 40.[4]
Akodon spegazzinii was first described in 1897 from Salta Province by Oldfield Thomas on the basis of a collection made in late 1896 or early 1897 by mycologist Carlos Luigi Spegazzini, after whom the species was named.[5] Four years later, Joel Asaph Allen named Akodon tucumanensis from Tucumán Province, comparing it to various species now synonymized under Abrothrix olivaceus.[6] Thomas named an additional species, Akodon alterus, from La Rioja Province in 1919, and considered it closely related to A. spegazzinii.[7] A fourth species, Akodon leucolimnaeus, was described by Ángel Cabrera from Catamarca Province in 1926, but after 1932 it was associated with Akodon lactens (now Necromys lactens) as a subspecies.[8]
In 1961, Cabrera listed both spegazzinii and tucumanensis as subspecies of Akodon boliviensis, with alterus as a full synonym of A. boliviensis tucumanensis.[4] In 1990, Philip Myers and colleagues reviewed the Akodon boliviensis species group. They provisionally kept Akodon spegazzinii as a species separate from A. boliviensis, with tucumanensis as a subspecies, and suggested that alterus was likely related to spegazzinii and tucumanensis.[9] Subsequently, the treatment of these species in systematic works became variable. A 1992 paper suggested that alterus and tucumanensis were, at best, very similar to each other,[10] but in 1997, Michael Mares and colleagues listed each of the three as distinct species in a compendium of the mammals of Catamarca, citing differences in habitat and fur coloration.[11] They were followed by Mónica Díaz and Rubén Bárquez in 2007, among others.[12] In 2000 Díaz and colleagues listed alterus and tucumanensis as subspecies of spegazzinii in a review of the mammals of Salta.[13] Guy Musser and Michael Carleton, in the 2005 third edition of Mammal Species of the World, also considered the three to represent the same species,[4] as did Ulyses Pardiñas and colleagues in a 2006 review of Argentinean Akodontini.[14] Meanwhile, Carlos Galliari and Pardiñas had recognized Akodon leucolimnaeus as a true Akodon, not a Necromys, in 1995. Although associated with the Akodon boliviensis group, its precise status remained unclear.[15] The common name "Catamarca akodont" was proposed for this species.[8]