Mitochondrial genetic variability of Didelphis albiventris (Didelphimorphia, Didelphidae) in Brazilian localities.

Didelphis albiventris is a well-known and common marsupial. Due to its high adaptability, this very widespread generalist species occurs under various environmental conditions, this even including protected regions and disturbed urban areas. We studied a 653 bp fragment of cytochrome oxidase c (COI) from 93 biological samples from seven Brazilian localities, with linear distances ranging between 58 and about 1800 km to analyze the effects of geographic distances on variability and genetic differentiation. The haplotype network presented nine haplotypes and two genetic clusters compatible with the two most distant geographic areas of the states of Minas Gerais, in the southeast, and Rio Grande do Sul, in the extreme south. As each cluster was characterized by low nucleotide and high haplotype diversities, their populations were obviously composed of closely related haplotypes. Surprisingly, moderate to high F(ST) differentiation values and a very weak phylogeographic signal characterizes interpopulation comparisons within Minas Gerais interdemes, these being correlated with the presence of privative haplotypes. On a large rgeographic scale, a comparison between demes from Minas Gerais and Rio Grande do Sul presented high F(ST) values and a robust phylogeographic pattern. This unexpected scenario implies that mtDNA gene flow was insufficient to maintain population cohesion, reflected by the observed high differentiation.

Cryptic speciation in Brazilian Epiperipatus (Onychophora: Peripatidae) reveals an underestimated diversity among the peripatid velvet worms.

BACKGROUND: Taxonomical studies of the neotropical Peripatidae (Onychophora, velvet worms) have proven difficult, due to intraspecific variation and uniformity of morphological characters across this onychophoran subgroup. We therefore used molecular approaches, in addition to morphological methods, to explore the diversity of Epiperipatus from the Minas Gerais State of Brazil. METHODOLOGY/PRINCIPAL FINDINGS: Our analyses revealed three new species. While Epiperipatus diadenoproctussp. nov. can be distinguished from E. adenocryptussp. nov. and E. paurognostussp. nov. based on morphology and specific nucleotide positions in the mitochondrial cytochrome c oxidase subunit I (COI) and small ribosomal subunit RNA gene sequences (12S rRNA), anatomical differences between the two latter species are not evident. However, our phylogenetic analyses of molecular data suggest that they are cryptic species, with high Bayesian posterior probabilities and bootstrap and Bremer support values for each species clade. The sister group relationship of E. adenocryptussp. nov. and E. paurognostussp. nov. in our analyses correlates with the remarkable morphological similarity of these two species. To assess the species status of the new species, we performed a statistical parsimony network analysis based on 582 base pairs of the COI gene in our specimens, with the connection probability set to 95%. Our findings revealed no connections between groups of haplotypes, which have been recognized as allopatric lineages in our phylogenetic analyses, thus supporting our suggestion that they are separate species. CONCLUSIONS/SIGNIFICANCE: Our findings suggest high cryptic species diversity and endemism among the neotropical Peripatidae and demonstrate that the combination of morphological and molecular approaches is helpful for clarifying the taxonomy and species diversity of this apparently large and diverse onychophoran group.

Inbreeding and PKU allele frequency: Estimating by microsatellite approaches.

UNLABELLED: Estimates of allele frequencies for recessive diseases are generally based on the frequency of affected individuals (q(2)). However, these estimates can be strongly biased due to inbreeding in the population. OBJECTIVES: The purpose of this study was to gain a better understanding of how inbreeding in the Minas Gerais State population affects phenylketonuria (PKU) incidence in the state and to determine the inbreeding coefficient based on microsatellites. METHODS: Inbreeding coefficients of samples of 104 controls and 76 patients with PKU were estimated through a microsatellite approach. Besides, the amount and distribution of genetic variation within and among patients with PKU and control samples were characterized. RESULTS: No genetic differentiation was observed between the samples. However, the Fis value found for samples of patients with PKU (0.042) was almost 15 times higher than that found among controls (0.003). When corrected by the inbreeding coefficient found among the controls, the PKU allele frequency decreased to 0.0057. CONCLUSIONS: The results enables us to infer that at least 35% of the PKU recessive homozygotes from the Minas Gerais population could be due to consanguineous marriages and suggest that microsatellites can be an useful approach to estimate inbreeding coefficients.

Brief communication: Admixture analysis with forensic microsatellites in Minas Gerais, Brazil: the ongoing evolution of the capital and of an African-derived community.

We report the estimated allele frequencies for 13 and 14 microsatellite loci in two populations of Minas Gerais, Brazil as follows: Belo Horizonte (the capital) and Marinhos (an African-derived community). Analysis of the African, Amerindian, and European genetic contributions to both populations, together with historical information, revealed distinct differences between the two populations. Estimates for Belo Horizonte revealed a higher-European (66%) than African (32%) contribution, and a minimal Amerindian contribution. These results are consistent with the peopling of the city mainly by people from the Minas Gerais hinterland, a people highly admixed but with more European ancestry. Estimates for Marinhos confirmed the high-African component of the population. However, a temporal analysis of two datasets-CURRENT (representing the population living in Marinhos today) and ORIGINAL (representing families, who have lived in Marinhos since the onset of the 20th century),-identified a diminishing of the population's African ancestry from 92% in the ORIGINAL group to 67% in the CURRENT group. This change is here interpreted as a consequence of the growing migration into the village of people with more European ancestry and subsequent admixture with the local population.