Genetic diversity and relatedness within and between species of the genus Oligoryzomys (Rodentia; Sigmodontinae)

Abstract

A RAPD analysis on six species of the rodent genus Oligoryzomys trapped in a wide area (ranging from 01° N to 32° S) of Brazilian territory was performed in order to determine the levels of genetic variability within and between its populations and species. One-hundred and ninety-three animals were collected in 13 different sites (corresponding to 17 samples) located at Pampas, Atlantic Rain Forest, Cerrado, and Amazon domains. Oligoryzomys sp., O. nigripes (8 populations), O. flavescens (4 populations), O. moojeni, O. stramineus, and O. fornesi were the taxa analyzed. Of the 20 primers tested, 4 generated a total of 75 polymorphic products simultaneously amplified in 151 specimens. Various diversity estimators analyzed showed considerable differences between species and populations, indicating a great genetic variation occurring in the Oligoryzomys taxa investigated. A cluster analysis was made using Nei´s standard genetic distances, however, it did not correlate the genetic heterogeneity of the species and populations with the geographical areas.Keywords: RAPD, DNA polymorphisms, Oligoryzomys, genetic distances, population genetics. Diversidade e relações genéticas dentro e entre espécies do gêneroOligoryzomys (Rodentia; Sigmodontinae) ResumoForam realizadas análises com RAPD em seis espécies de roedores do gênero Oligoryzomys capturados em uma ampla área (estendendo-se de 01° N a 32° S) do território brasileiro com o objetivo de determinar os níveis de variabilidade genética dentro e entre as populações e espécies. Cento e noventa e três animais foram coletados em 13 locais diferentes (correspondendo a 17 amostras) localizados nos Pampas, Floresta Atlântica, Cerrado e Amazônia.

Comparison between Oligoryzomys nigripes and O. flavescens by RAPD and genetic diversity in O. nigripes (Rodentia, Cricetidae)

“…There was a separation among karyotyped individuals, proven to be O. flavescens and O. nigripes, which corroborates the fact that the molecular markers based on RAPD are capable of genetically separating these two species. Such results are also in agreement with those found by Trott et al (2007), because these authors were able to distinguish 6 species and 13 populations using RAPD markers, thus showing that the taxa of Oligoryzomys are genetically different.…”

“…The first group corresponds to the two karyotyped specimens identified as Oligoryzomys flavescens, and the second one represents the other individuals, including those karyotyped defined as Oligoryzomys nigripes, a clear grouping between the members of this group not occurring with regard to the collecting area. This result indicates the capacity of the RAPD molecular markers in separating these two species, a result also obtained by Trott et al (2007), allowing the identification of the individuals analysed in the second part of this work. Besides, a clear separation was noted for the individual Euryoryzomys russatus, collected at Horto Florestal Erechim-RS, and included in the analysis as external standard.…”

“…Nevertheless, genetic relationships among populations of Oligoryzomys coming from such data seem not to be dependent on geographical distances nor influenced by rivers acting as reproductive barriers. Trott et al (2007) demonstrated that several diversity estimations presented considerable differences among the species and populations, hence pointing to a great genetic variety among taxa of Oligoryzomys investigated. The grouping analysis using the genetic distance method by Nei, however, did not correlate the genetic heterogeneity of species and populations with the geographical areas, corroborating the results found in this work.…”

“…Besides, a clear separation was noted for the individual Euryoryzomys russatus, collected at Horto Florestal Erechim-RS, and included in the analysis as external standard. Trott et al (2007), in investigating RAPD markers of the genus Oligoryzomys distributed in different biomes of Brazil, used a total of 75 polymorphic products simultaneously amplified in 151 specimens and observed that there is a great genetic variation among the taxa of Oligoryzomys investigated. However, they also noted that among the species of this genus, O. nigripes and O. flavescens presented the smallest genetic distance.…”

“…Myers et al (1995), in studying the cytochrome b sequence, also found little evidence in the difference among Oligoryzomys populations investigated. Trott et al (2007) analysed the diversity and genetic relations inside and among species of the genus Oligoryzomys and observed considerable differences among populations and species thus indicating the presence of a great genetic variety among the taxa of Oligoryzomys investigated. Nevertheless, grouping analysis employing the genetic distance method of Nei did not correlate genetic heterogeneity of species and populations with geographical areas.…”