Neotropical porcupines

36 p. : ill. (some col.) ; 26 cm.Includes bibliographical references (p. 32-35).Neotropical porcupines of the Coendou vestitus group consist of four small-bodied species from northwestern South America that are hypothesized to form a clade on the basis of their unique dorsal pelage composition. In addition to soft wool and barbed quills--hair types widely shared by other erethizontids--the dorsal pelage of vestitus-group porcupines includes what may be called bristle-quills: long, thin, unbarbed quills with flexible tips. The group includes Coendou vestitus Thomas, 1899; C. pruinosus Thomas, 1905; and two new species. The latter provide the first documented records of small porcupines from western Amazonia, where only large porcupines (C. prehensilis and C. bicolor) were previously known. Other small porcupines probably remain to be discovered in Amazonia, where hydroelectric dam projects offer unique (if unfortunate) faunal-sampling opportunities

Karyological analysis of Proechimys cuvieri and Proechimys guyannensis (Rodentia, Echimyidae) from central Amazon

The aim was to characterize the karyotype of rodents of the genus Proechimys from three localities in the central Brazilian Amazon, in the search for new markers that might shed light on our understanding of the taxonomy and evolutionary history of this taxon. Two karyotypes were found, viz., 2n = 28, FN = 46 in individuals from the NRSP (Cuieiras River) and REMAN (Manaus), and 2n = 46, FN = 50 in individuals from the Balbina Hydroelectric Plant. While individuals with the karyotype with 2n = 28 chromosomes were morphologically associated with Proechimys cuvieri, their karyotype shared similarities with those of the same diploid number in two other regions. Although three karyotypes are described for Proechimys cuvieri, no geographic distribution pattern that defined a cline could be identified. Based on the morphological examination of voucher specimens and additional results from molecular analysis, the karyotype with 2n = 46 and FN = 50 could be associated with P. guyannensis

Riverine barriers and gene flow in amazonian saddle-back tamarins

We describe patterns of genotypic and phenotypic variation in saddle-back tamarin (Saguinus fuscicollis) populations along the central and upper Rio Jurua, western Brazilian Amazonia. The genetic data are sequence haplotypes of the mitochondrial cytochrome b gene; phenotypic data are pelage colour variants that define sharply demarcated subspecies of this extremely variable tamarin species. We show that gene flow occurs between adjacent subspecies, but that this phenomenon is restricted to the headwater section of the river, which is consistent with expectations from the riverine barrier hypothesis. In this model, the major first-order tributaries of the Amazon form effective barriers to dispersal, with between-bank gene flow limited to the narrowed sections of headwater streams and parallel divergence increasing along both banks from the headwaters to the mouth of a given river. In meandering rivers such as the Rio Juru�, we suggest passive transfer through river channel dynamics as the main mechanism permitting genetic contact between populations on opposite banks of the river. Finally, we argue that in the case of plant and animal species that are largely restricted to unflooded (terra firme) forests, such as tamarins, seasonally flooded (v�rzea) forest can operate as a critical additional barrier to between-bank gene flow

The simultaneous diversification of South American Echimyid rodents (Hystricognathi) based on complete cytochrome b sequences

Variation in the complete nucleotide sequence of the mitochondrial cytochrome b gene was examined for 32 individuals representing 12 supraspecific taxa of South American rodents of the family Echimyidae (Hystricognathi). Representative genera of four other New World hystricognath families, the Old World porcupine Hystrix, and the myomorph murid rodents Rattus and Mus were used as outgroups in phylogenetic reconstructions. Monophyly of the family Echimyidae is strongly supported, a result fully consistent with existing morphological and paleontological data relative to the taxa examined. However, relationships among most supraspecific taxa within the family are poorly resolved. Poor resolution appears not to result from lack of data, but to a rapid, nearly simultaneous divergence of most Recent taxa. Generic groupings that are moderately to strongly supported include the tree rats of the Brazilian Atlantic Forest (Nelomys) and Amazonia (Echimys, Makalata) and the Amazonian arboreal spiny rats Mesomys and Lonchothrix. However, the two subgenera of the terrestrial spiny rats, Proechimys, do not form a monophyletic unit, and elevation of the Atlantic Forest Trinomys to generic status is supported. The genus Hoplomys is closely related to Proechimys (sensu stricto), a finding supported by other molecular data