Estudios genético-poblacionales en el género Calomys (Rodentia, Sigmodontinae, Phyllotini), con especial referencia a C. musculinus, reservorio natural del virus Junin

GARDENAL, C.N; CHIAPPERO, M.B.; GONZÁLEZ ITTIG, R.E.; GARCÍA, B.A.

Biología y Ecología de Pequeños Roedores en la Región Pampeana de Argentina, enfoques y perspectivas.

Universidad Nacional de Córdoba

Lugar: Córdoba; Año: 2010; p. 59 - 86

The muroid rodent Calomys musculinus is the natural reservoir of Junin virus, the etiological agent of Argentine hemorrhagic fever (FHA), an emerging disease in the central-eastern area of the country. In order to contribute to the understanding of the processes influencing the expansion of the endemic area of FHA, we examined the genetic structure of the populations of the host. Similar studies were conducted in a related sympatric species, Calomys laucha. Several genetic markers were employed: isozymes, RAPDs-PCR and PCR-RFLP of the D-loop region of mitochondrial DNA. Some of those markers were species-specific, which was very useful for a precise taxonomic identification of individuals captured in the field. Mean heterozygosity estimates were, in both species, among the highest reported for rodents; this result is on line with predictions based on ecological, demographic and life history characteristics of the species. In C. musculinus, mean genetic differentiation among populations was low but significant; there was no correlation between genetic and geographic distances and scatter of pairwise comparisons suggested that, at a regional scale, genetic drift is more influential than on-going gene flow. The phylogeographic study based on 24 haplotypes detected in 16 wild populations, covering most of the distribution area of the species, confirmed this result and supported the hypothesis of a recent range expansion of the populations of C. musculinus in the Humid Pampa. Effective population sizes (Ne) were estimated by the pseudo-likelihood method in two populations 280 km apart in central Argentina. Both populations experienced marked seasonal changes in relative density and in Ne. After low density periods, mixing of surviving individuals coming from different demes may play an important role in the maintenance of variability and recovery of  Ne in C. musculinus populations. In C. laucha, temporal fluctuations in allele frequencies were also observed as a consequence of demographic changes. Relationships between migration patterns of C. musculinus  and the potential spread of the FHA are discussed.