Gene flow among populations of Oligoryzomys flavescens (Rodentia: Muridae) from central Argentina

CHIAPPERO, M.B.; CALDERÓN, G.E.; GARDENAL, C.N.

San Antonio

Congreso; 9th International Congress on Genes, Gene Families and Isozymes; 1997

Southwest Foundation for Biomedical Research

In species acting as host of infectious agents, knowledge of the extent of gene flow beween populations has particular interest, since the expansion of different infectious diseases is usually related to the dispersal of the host. We have estimated levels of gene flow among populations of the sigmodontine rodent Oligoryzomys flavescens, in which high titers of antibodies against a Hantavirus producing a severe pulmonar syndrome in Argentina have been detected. Enzyme polymorphism was studied by means of starch gel electrophoresis on then populations from the area where human cases of Hantavirus have occurred. Genetic differentiation among populations was estimated by means of F-statistics. Gene flow between populations was calculated from FST values with the equation Nm=(1/FST-1)/4. To analyze the patterns of dispersal in this species, the relationship of population pairwise log Nm and log geographic distance was examined. An important degree of genetic variability in all the samples was found. FST (mean=0,038) and Nm (15,27) values show high levels of gene flow among populations. The lack of correlation between Nm and geographic distance would indicate that this species has recently colonized the area. The northernmost population, located on the margin of a great river, shows very high levels of gene flow with the downstream populations despite the large geographic distances. Passive transport of animals down the river by floating plants would promote unidirectional gene flow. This fact, and the highest mean heterozygosity of that northernmost population suggest it is a center of dispersal within the species' range.