Genetic structure and dispersal in brown rats (Rattus norvegicus) in an urban ecosystem.

CUETO, G. R.; GUZMAN, N; LIA, V.; CAVIA, R.; SUAREZ, O.

Mendoza, Argentina

Congreso; 10 th International Mammalogical Congreso; 2009

International Federation of Mammalogists - IFM and Sociedad Argentina para el Estudio de los Mamíferos - SAREM

To investigate genetic variation we used 10 microsatellite markers in 91 R. norvegicus trapped in 9 sites throughout Buenos Aires city, Argentina. Fifty six alleles were registered (mean per locus: 5.6). One population located closed to the harbor showed the highest number of exclusive alleles (5), followed by two populations located in the Southwest, with 3 and 1 alleles respectively. Allele frequency was calculated only for 5 populations with at least 15 analized individuals. Two populations were from shantytowns (one near the port and the other from the west of the city) and the three remains from parklands (located in the north, in the south and in the southwest of the city). The Fst index showed low differentation levels among populations located closed to the rivers (De la Plata and Riachuelo), although they were geographically distant (Correlation Fst vs. geographic distance: Mantel`s test P>0.1; Correlation Fst vs. differences in the distance to the river: Mantel`s test P=0.03). Genetic variability of the populations decreased with the increase of the distance to the port. This relationship was registered for the mean expected heterozygosity He (R2=0.656), for the mean number of alleles per locus A (R2=0.673), and for the allelic richness R (R2=0.662). The population located closed to the harbor showed the biggest values in Fis. We detected a significant heterozygote deficit only in this population. This results couldsuggest that near the harbor several populations of R. norvegicus from different origins coexist, generating a mix of populations where the allelic frequencies has not been homogenized yet. We conclude that a) the rats coming from different parts of the world enter to Buenos Aires city through the port, and b) the habitats associated to the rivers could act as corridors allowing dispersal of this specie in the city.