Evolutionary diversification ofPhyllomys(Rodentia: Echimyidae) in the Brazilian Atlantic Forest

Diversification of Amazonian spiny tree rats in genus Makalata (Rodentia, Echimyidae): Cryptic diversity, geographic structure and drivers of speciation

Amazonian mammal diversity is exceptionally high, yet new taxonomic discoveries continue to be made and many questions remain for understanding its diversification through time and space. Here we investigate the diversification of spiny rats in the genus Makalata, whose species are strongly associated with seasonally flooded forests, watercourses and flooded islands. We use a biogeographical approach based on a mitochondrial cytochrome b gene through divergence time estimation and reconstruction of ancestral areas and events. Our findings indicate an ancient origin of Makalata for the Guiana Shield and Eastern Amazonia as ancestral area. A first cladogenetic event led to a phylogeographic break into two broader clades of Makalata through dispersal, implying a pattern of western/Eastern Amazonian clades coinciding with the Purus Arch (middle Miocene). Most of subclades we infer originated between the late Pliocene to the early Pleistocene, with few recent exceptions in the early Pliocene through dispersal and vicariant events. The hypothesis of rivers as dispersal barriers is not corroborated for Makalata, as expected for mammalian species associated with seasonally flooded environments. We identify two key events for the expansion and diversification of Makalata species: the presence of geologically stable areas in the Guiana and Brazilian shields and the transition from lacustrine conditions in western Amazonia (Acre system) to a river system, with the establishment of the Amazon River transcontinental system and its tributaries. Our results are congruent with older geological scenarios for the Amazon basin formation (Miocene), but we do not discard the influence of recent dynamics on some speciation events and, mainly, on phylogeographic structuring processes.

Mammals of a restinga forest in Mataraca, Paraíba, northeastern Brazil, and its affinities to restinga areas in Brazil

Abstract The Restinga forests are plant formations associated to the Atlantic Forest which still have not been much studied in terms of their mastofauna. The objective of the present work was to list for the first time the mammal species found in a Restinga on northeastern Brazil and show the similarities on species composition to other areas of the same environment and of Atlantic Forest. Our records were based on several complementary approaches: field survey, interviews, and museum collections. Subsequently, we performed similarity analysis between Restinga areas along Brazil and Atlantic Forest areas. We found a total of 30 species of mammals distributed in 28 genera, 16 families and 7 orders for Restinga of Mataraca. Species richness was similar to other Restinga areas and similarity analyzes pointed out that Restingas are more closely related to adjacent Atlantic Forest areas than to other Restingas in the country. This suggests that Restingas do not exhibit an autochthone fauna, but rather a faunal subsample of neighbor Atlantic Forest. Therefore, conservations policies for the Restinga habitat depends not only on actions focused on this habitat, but on initiatives that encompass nearby Atlantic Forest remnants, allowing the connectivity between these habitats.

Syntopy of cryptic Phyllomys (Rodentia: Echimyidae) species: description of the karyotype of Phyllomys nigrispinus and an expansion of the geographic distribution of Phyllomys sulinus

The echimyid rodents of the genus Phyllomys are medium-sized arboreal spiny rats endemic to the Atlantic Forest of Brazil. The genus is currently composed of 13 species, although there are at least four other undescribed species. The ecology, zoogeography and diversity of the genus are still poorly understood. Here, we provide the first record of Phyllomys sulinus from the Brazilian state of Rio de Janeiro, based on a specimen collected in the Serra da Bocaina National Park, which extends the known geographic range of the species approximately 130 km to the northeast. At this site, P. sulinus occurred in syntopy with the cryptic Phyllomys nigrispinus. We describe the karyotype of P. nigrispinus for the first time and identify two different diploid numbers (2n=84 and 85). We also conducted a molecular analysis of the cytochrome b gene of five specimens, which we identified by phylogenetic reconstruction. Our findings reinforce the importance of molecular data, such as DNA sequences, and karyotypes for the differentiation of cryptic, syntopic species.

New karyotypes of Atlantic tree rats, genus Phyllomys (Rodentia: Echimyidae)

Phyllomys (Echimyidae, Rodentia) is a genus of Neotropical rodents with available cytogenetic data restricted to six out of 13 species, mainly based on simple staining methods, without detailed analyses. In this work, we present new karyotypes for Phyllomys lamarum (diploid number 2n = 56, fundamental number or number of autosomal arms FN = 102) and Phyllomys sp. (2n = 74, FN = 140) from the state of Minas Gerais, southeastern Brazil. We provide the first GTG- and CBG-banding patterns, silver-staining of the nucleolar organizer regions (Ag-NORs), and fluorescence in situ hybridization (FISH) with telomeric and 45S rDNA probes of Phyllomys. In addition to examining their chromosomes and phenotypic characters, we sequenced mitochondrial DNA from the specimens analyzed to confirm their taxonomic identification. The comparison of the distinctive chromosome complements of our specimens with those of other species of Phyllomys already published allowed us to conclude that chromosome data may be very useful for the taxonomy of the genus, as no two species analyzed presented the same diploid and fundamental numbers (2n and FN).

Transitions between Andean and Amazonian centers of endemism in the radiation of some arboreal rodents

Background

The tropical Andes and Amazon are among the richest regions of endemism for mammals, and each has given rise to extensive in situ radiations. Various animal lineages have radiated ex situ after colonizing one of these regions from the other: Amazonian clades of dendrobatid frogs and passerine birds may have Andean ancestry, and transitions from the Amazon to Andes may be even more common. To examine biogeographic transitions between these regions, we investigated the evolutionary history of three clades of rodents in the family Echimyidae: bamboo rats (Dactylomys-Olallamys-Kannabateomys), spiny tree-rats (Mesomys-Lonchothrix), and brush-tailed rats (Isothrix). Each clade is distributed in both the Andes and Amazonia, and is more diverse in the lowlands. We used two mitochondrial (cyt-b and 12S) and three nuclear (GHR, vWF, and RAG1) markers to reconstruct their phylogenetic relationships. Tree topologies and ancestral geographic ranges were then used to determine whether Andean forms were basal to or derived from lowland radiations.

Results

Four biogeographic transitions are identified among the generic radiations. The bamboo rat clade unambiguously originated in the Amazon ca. 9 Ma, followed by either one early transition to the Andes (Olallamys) and a later move to the Amazon (Dactylomys), or two later shifts to the Andes (one in each genus). The Andean species of both Dactylomys and Isothrix are sister to their lowland species, raising the possibility that highland forms colonized the Amazon Basin. However, uncertainty in their reconstructed ancestral ranges obscures the origin of these transitions. The lone Andean species of Mesomys is confidently nested within the lowland radiation, thereby indicating an Amazon-to-Andes transition ca. 2 Ma.

Conclusions

Differences in the timing of these biogeographic transitions do not appear to explain the different polarities of these trees. Instead, even within the radiation of a single family, both Andean and Amazonian centers of endemism appear enriched by lineages that originated in the other region. Our survey of other South American lineages suggests a pattern of reciprocal exchange between these regions—among mammals, birds, amphibians, and insects we found no fewer than 87 transitions between the Andes and Amazon from Miocene-Pleistocene. Because no clear trend emerges between the timing and polarity of transitions, or in their relative frequency, we suggest that reciprocal exchange between tropical highland and lowland faunas in South America has been a continual process since ca. 12 Ma.