Microsatellite genotyping from faeces of Lontra longicaudis from southern Brazil

Laura I Weber,Cintia G Hildebrand,José A Levy,Elton P Colares,Anderson Ferreira,Gustavo Pedarassi

doi:10.1590/s0073-47212009000100001

Abstract

A genetic study of the neotropical river otter Lontra longicaudis (Olfers, 1818), which has an unknown conservation status, was carried out at the Taim Ecological Station and the margins of the Vargas stream, Rio Grande do Sul, southern Brazil. Faecal samples were collected, and DNA was extracted using a silica-guanidine method. Five microsatellite loci were amplified using PCR with heterologous primers previously described for Lutra lutra (Linnaeus, 1758). Sixteen faecal samples out of 29 from Taim and 11 out of 14 from Vargas stream margins contained enough DNA for genetic analysis. A total of 49 different alleles were found at both localities, from which 18 were exclusively found in individuals from Taim and 17 were exclusives from Vargas individuals. The most common allele was the same at both locations for three loci (Lut715, Lut733, and Lut818). A high level of genetic diversity was found at both sites (NeTaim=4.1, HoTaim=0.299, HeTaim=0.681; NeVargas=4.9, HoVargas=0.355, HeVargas=0.724), being higher at the Vargas stream site. A high and significant level of heterozygote deficiency was observed at most loci according to the χ2 test. The homogeneity χ2 test (P<0.001) showed that there were significant differences in the allele frequencies between the two locations. Genotyping for more than one locus was possible in 81.5% of samples, from which only 37% were possible to genotype for more than three loci. A low degree of relatedness was found among individuals from Taim (R=0.055±0.310), but an even lower value of relatedness was found at the Vargas site (R= -0.285±0.440). The significant degree of differentiation (I=0.890; F ST=0.059) found between Taim and Vargas individuals suggests that there is more than one population of otters in the southern extreme of Brazil, which probably are associated with the water body systems found in this region, the Mirim and the Caiuvá/Flores/Mangueira Lagoons. The high genetic diversity and low relatedness found at the Vargas stream, lead us to believe that the Vargas stream may be acting as a corridor between these water bodies for otter dispersion.

Highlights

As L. longicaudis has been considered a subspecies of L. canadensis by some authors (HERSHKOVITZ, 1972; DAVIS, 1978), and more recently, studies have shown that these two species are very closely related (KOEPFLI & WAYNE, 1998; 2003), we expected that these primers would be useful for studying the neotropical otter L. longicaudis
16 faecal samples from the Taim and 11 from the Vargas stream margins contained enough DNA to proceed with genetic analysis
The Lut715 microsatellite had the largest number of alleles at the Taim, while the Lut457 microsatellite had the most alleles at the Vargas stream

Summary

Introduction

Dezesseis amostras de fezes de um total de 29 coletadas no Taim e onze das 14 obtidas no arroio Vargas contiveram DNA suficiente para prosseguir com a analise genética. O grau significativo de diferenciação genética (I=0,890; FST=0,059) entre os indivíduos do Taim e do arroio Vargas sugere a existência de mais de uma população de lontras no extremo sul do Brasil, que provavelmente estejam associadas aos diferentes corpos de água existentes nesta região: a Lagoa Mirim e o sistema de lagoas Cauivá/Flores/Mangueira. A number of primers suitable for the amplification of microsatellites in the Eurasian otter Lutra lutra (Linnaeus, 1758) were described by DALLAS & PIERTNEY (1998) These primers were useful for analyzing genetic variability in the river otter Lontra canadensis (BLUNDELL et al, 2002b) and sea otter Enhydra lutris (Linnaeus, 1758) (LARSON et al, 2002a,b). Our second goal was to study the genetic composition of L. longicaudis at two geographical sites in the south of Brazil, in order to evaluate population division, genetic diversity, and dispersion of individuals between the protected area of the Taim Ecological Station and the unprotected surroundings of the Vargas stream

Methods

Results

Conclusion