Phyogeography of two species of the genus Eligmodontia (Rodentia: Cricetidae) in Argentinean Patagonia

DA SILVA, C.; D'ELÍA, G.; PARDIÑAS, U.F.J.; LESSA, E.

Mendoza

Congreso; 10 International Mammalogical Congress (Mendoza, Argentina); 2009

IFM-SAREM

The first specimen of Eligmodontia was acquired by Charles Darwin in 1835 at Bahía Blanca (Argentina), during his five-year journey on the HMS Beagle. It was formally described by George R. Waterhouse as Mus elegans in February 1837, just weeks after the formal description of E. typus by Frédéric Cuvier, from a specimen that he had received from Buenos Aires and which was collected six months after Darwin's. The two taxa were later synonymized and represent the same species. Actualy this genus consists of six species that inhabits arid and semiarid regions of South America. The species E. typus (habitat: lowlands of Patagonia) and E. morgani (habitat: South and South-west of Patagonia) inhabit the southern distribution of this genus, a poorly studied area in a biogeographical sense. This study is framed in the Pleistocene Refugia Theory, which posits that the main factor in speciation is the geographical isolation caused by the retraction of the habitats during glacial period. Our sample is a total of 68 specimens (E. morgani: 25, E. typus: 43) from 16 localities (Provinces of Chubut, Río Negro and Santa Cruz; Argentina) whose cytochrome b genes were sequenced. We found sympatry in two localities (Estancia Los Manantiales, Chubut and Estancia Cerro del Paso, Santa Cruz). Phylogenetic analyses resulted in basal polytomies in each species, which also showed limited geographical structure. Tests of neutrality were negative and significant in the following cases: E. morgani (Tajima´s D: -1.73686) and E. typus (Tajima´s D: -2.18740, and Fu’s Fs: -7.00013). These results suggest a history of recent demographic expansion, possibly associated with changes in habitat availability in these species, in agreement with the Pleistocene Refugia Theory.