Genetic differentiation in geographically close populations of the water rat Nectomys squamipes (Rodentia, Sigmodontinae) from the Brazilian Atlantic Forest

• Published in: Genetics and molecular biology Vol. 26; no. 4; pp. 403 - 410
• Main Authors: Maroja, L.S., Almeida, F.C., Seuánez, H.N.
• Format: Journal Article
• Language: English
• Published: Sociedade Brasileira de Genética 01-12-2003
• Subjects: BIOCHEMISTRY & MOLECULAR BIOLOGY; GENETICS & HEREDITY; microsatellites; migration; Nectomys squamipes; population genetics; Schistosoma mansoni host; Sigmodontinae; Brazil; microsatellites; migration; population genetics; Sigmodontinae; Schistosoma mansoni host
• ISSN: 1415-4757; 1678-4685; 1415-4757; 1678-4685
• DOI: 10.1590/S1415-47572003000400002

We examined the genetic structure and the effects of a bottleneck in populations of the water rat Nectomys squamipes, a primary host of Schistosoma mansoni. Eight microsatellite loci were studied in 7 populations from the Sumidouro region of the Brazilian state of Rio de Janeiro. Our data, covering a four-year period during which a bottleneck occurred, revealed substantial variation (6-31 alleles per locus) and high levels of both observed (0.718-0.789) and expected (0.748-0.832) heterozygosity. Most populations were in Hardy-Weinberg equilibrium without linkage disequilibrium between loci. Overall average genetic differentiation between populations (estimated with the F sub(ST) (q) and R sub(ST) (r) analogues was 0.037 for q and 0.060 for r. There was significant allelic and genotypic differentiation between populations, especially in pairwise comparisons that included the most geographically isolated population. Direct migration estimates showed a low rate of migration, indicating that infected N. squamipes populations had a limited ability to spread S. mansoni. When the pre- and post-bottleneck populations were compared there was no detectable reduction in heterozygosity or allele number, although a significant excess of heterozygosity was detected in the post-bottleneck population.