Genetic diversity in different populations of sloths assessed by DNA fingerprinting

Genetic assessment of the Atlantic Forest bristle porcupine, Chaetomys subspinosus (Rodentia: Erethizontidae), an endemic species threatened with extinction

The bristle-spined porcupine, Chaetomys subspinosus, an endemic rodent from Atlantic Forest, was considered to be abundant in the recent past, but population reductions due to habitat loss and expansion of human activities caused this species to be included in the "vulnerable" category of the World Conservation Union Red List. We performed the first genetic assessment in natural populations of this focal species along its geographical distribution. Thirty-five non-invasive samples (hair) were collected from three natural populations in the Brazilian States of Sergipe, Bahia and Espírito Santo. Genetic similarity obtained by Jaccard's index, based on dominant RAPD and ISSR markers, varied between 25 and 100%. Four clusters, mainly coincident with the geographical distribution of the populations, were observed. Analysis of molecular variance based on 47 polymorphic loci showed that there was 15.99% genetic variability among populations and 84.01% within populations. The estimated genetic structure among populations (Φ(ST)) was 0.16. The populations may have formed a continuum along the past distribution of the Atlantic rainforest but historical events of human occupation resulted in recent divergence among sampled populations.

Species identification and chromosome variation of captive two-toed sloths

Two-toed sloth species, Linnaeus's and Hoffmman's, are frequent residents of zoo collections in North America. However, species identification has always been problematic because of their large overlap in external morphology, which represents an obstacle to the captive breeding program. We describe here a PCR-based technique that allows species identification of two-toed sloths without requiring sequencing, by using a mitochondrial marker (COI gene) and restriction enzyme assay. We also report intra- and inter-specific patterns of chromosome variation in captive two-toed sloths. Molecularly, we identified 22 samples of Linnaeus's and Hoffmman's two-toed sloths corresponding to 14 and 8 individuals, respectively. One animal was identified as a hybrid using the nuclear gene Enam having alleles derived from both species. The chromosome number in Hoffman's two-toed sloths showed low variation ranging only between 50 and 51. In contrast, Linnaeus's two-toed sloths appeared to vary widely, with diploid numbers ranging from 53 to 67, suggesting distinct geographic groups. The species identification method presented here represents a low-cost easy-to-use tool that will help to improve management of the captive population of two-toed sloths.

Comparative Phylogeography of the Atlantic Forest Endemic Sloth (Bradypus torquatus) and the Widespread Three-toed Sloth (Bradypus variegatus) (Bradypodidae, Xenarthra)

The comparative phylogeographic study of the maned sloth (Bradypus torquatus) and the three-toed sloth (Bradypus variegatus) was performed using a segment of mitochondrial DNA (mtDNA) control region. We examined 19 B. torquatus from two regions and 47 B. variegatus from three distant regions of Atlantic forest. This first characterization of molecular diversity indicates a great diversity (B. torquatus: h = 0.901 +/- 0.039 and pi = 0.012 +/- 0.007; B. variegatus: h = 0.699 +/- 0.039 and pi = 0.010 +/- 0.006) and very divergent mitochondrial lineages within each sloth species. The different sampled regions carry distinct and non-overlapping sets of mtDNA haplotypes and are genetically divergent. This phylogeographic pattern may be characteristic of sloth species. In addition, we infer that two main phylogeographic groups exist in the Atlantic forest representing a north and south distinct divergence.