The forest refuge hypothesis (FRH) has long been a paradigm for explaining the extreme biological diversity of tropical forests. According to this hypothesis, forest retraction and fragmentation during glacial periods would have promoted reproductive isolation and consequently speciation in forest patches (ecological refuges) surrounded by open habitats. The recent use of paleoclimatic models of species and habitat distributions revitalized the FRH, not by considering refuges as the main drivers of allopatric speciation, but instead by suggesting that high contemporary diversity is associated with historically stable forest areas. However, the role of the emerged continental shelf on the Atlantic Forest biodiversity hotspot of eastern South America during glacial periods has been ignored in the literature. Here, we combined results of species distribution models with coalescent simulations based on DNA sequences to explore the congruence between scenarios of forest dynamics through time and the genetic structure of mammal species cooccurring in the central region of the Atlantic Forest. Contrary to the FRH predictions, we found more fragmentation of suitable habitats during the last interglacial (LIG) and the present than in the last glacial maximum (LGM), probably due to topography. We also detected expansion of suitable climatic conditions onto the emerged continental shelf during the LGM, which would have allowed forests and forest-adapted species to expand. The interplay of sea level and land distribution must have been crucial in the biogeographic history of the Atlantic Forest, and forest refuges played only a minor role, if any, in this biodiversity hotspot during glacial periods.T he extreme biological diversity of tropical forests has inspired and puzzled naturalists and scientists for centuries, and the forest refuge hypothesis (FRH) has long been one of the major paradigms to explain it. According to the FRH, forest retraction and fragmentation during glacial periods would have promoted isolation and consequently allopatric speciation in forest patches, or ecological refuges, surrounded by open habitats in the Amazon (1). Although originally based on climate fluctuations in the Pleistocene, the FRH was subsequently invoked for climate changes irrespective of the time period (2). The FRH was also applied to South America's Atlantic Forest (3), one of the topfive biodiversity hotspots on Earth (4). The FRH gained broad acceptance during the 1980s when empirical paleoecological data from neotropical rainforests were still lacking. Nevertheless, heavy criticism came upon the FRH because some paleobotanical data showed that forests had persisted throughout glacial cycles (5). As paleoclimatic models of species and habitats became widely used, recent studies revitalized the FRH, not by considering refuges as the main drivers of allopatric speciation, but instead by suggesting that high contemporary diversity and endemism are associated with historically stable Atlantic Forest areas (6).This hypothesis is ba...

Levels of reproductive skew vary in wild primates living in multimale groups depending on the degree to which high-ranking males monopolize access to females. Still, the factors affecting paternity in egalitarian societies remain unexplored. We combine unique behavioral, life history, and genetic data to evaluate the distribution of paternity in the northern muriqui (Brachyteles hypoxanthus), a species known for its affiliative, nonhierarchical relationships. We genotyped 67 individuals (22 infants born over a 3-y period, their 21 mothers, and all 24 possible sires) at 17 microsatellite marker loci and assigned paternity to all infants. None of the 13 fathers were close maternal relatives of females with which they sired infants, and the most successful male sired a much lower percentage of infants (18%) than reported for the most successful males in other species. Our findings of inbreeding avoidance and low male reproductive skew are consistent with the muriqui's observed social and sexual behavior, but the long delay (≥2.08 y) between the onset of male sexual behavior and the age at which males first sire young is unexpected. The allocation of paternity implicates individual male life histories and access to maternal kin as key factors influencing variation in paternaland grandmaternal-fitness. The apparent importance of lifelong maternal investment in coresident sons resonates with other recent examinations of maternal influences on offspring reproduction. This importance also extends the implications of the "grandmother hypothesis" in human evolution to include the possible influence of mothers and other maternal kin on male reproductive success in patrilocal societies.mating system | reproductive strategy | development | molecular ecology | Platyrrhini

All available published cytogenetic data show the presence of 28 different karyotypes in 311 specimens of A. cursor as an exceptional example of high karyotype variability in a single species. Our present sample of 116 animals collected in the rain forest of the Atlantic coast of the states of São Paulo and Bahia, Brazil, show 25 karyotype constitutions. The diploid number (2n) ranged from 16 to 14, and the number of autosomal arms (NF) from 26 to 18, because of centric fusion and pericentric inversions involving two autosome pairs, pericentric inversions in three other chromosome pairs, trisomy in the pair 7 and the presence of two XO females. Synaptonemal complex analysis, associated with data from experimental cross-breeding, suggested that heterozygous individuals for pericentric inversions have normal fertility. In this paper, we have reviewed the chromosomal data of this species, and have thus standardized the karyotype description and chromosome numbering. We discuss about karyotype evolution of Akodon cursor based on the frequency and constitution of karyotypes of all different geographical samples described so far in the literature.

In the present paper, we describe Juliomys ossitenuis, a new species of sigmodontine rodent from the Altantic forest biodiversity hotspot in South America. This new species can be distinguished from the two congeners by clear morphological, molecular, and karyological characters. Juliomys ossitenuis is known from rain and semi-deciduous forests above 800 meters of altitude in southeastern Brazil, ranging from the state of Espírito Santo to São Paulo. Molecular phylogenetic analyses based on the mitochondrial cytochrome b gene confirmed that members of this new species form a well-supported monophyletic group, highly divergent from the other two species in the genus.

Comparative studies among four species – Akodonazarae (2n = 38), A. lindberghi (2n = 42), A. paranaensis (2n = 44) and A. serrensis (2n = 46) – employing classic cytogenetics (C- and G-bands) and fluorescence in situ hybridization with telomeric (TTAGGG)_n sequencesare reported here. Non-telomeric signals in addition to the regular telomeric sites were detected in three species:A. azarae, A. lindberghi and A. serrensis. One interstitial telomeric site (ITS) was observed proximally at the long arm of chromosome 1 of A. azarae. The comparison of G-banding patterns among the species indicated that the ITS was due to a tandem fusion/fission rearrangement. Non-telomeric signals of A. lindberghi and A. serrensis were not related to chromosomal rearrangements; instead, the sequences co-localized with (i) heterochromatic regions of all chromosomes in A. serrensis; (ii) some heterochromatic regions in A. lindberghi, and (iii) both euchromatic and heterochromatic regions in the metacentric pair of A. lindberghi. These exceptional findings revealed that ITS in Akodon can be related to chromosomal rearrangements and repetitive sequences in the constitutive heterochromatin and that the richness of TTAGGG-like sequences in the euchromatin could be hypothesized to be a result of amplification of the referred sequence along the chromosome arms.