Ana Cristina Mendes-Oliveira

The role of remnants of Amazon savanna for the conservation of Neotropical mammal communities in eucalyptus plantations

In this study, we investigated the effects of the partial conversion of native Amazon savanna into a eucalyptus plantation on the richness, composition, and abundance of medium and large mammals. Considering these plantations as an integral component of a patchwork savanna landscape, we verified how the negative effects of these plantations can be buffered by the conservation of remnants of native habitat within their area. We analyzed the contribution of each type of Amazonian savanna to the maintenance of the mammalian fauna and the potential of eucalyptus plantations to substitute these native habitats. A total of 23 mammal species were recorded in line-transect surveys conducted within the conserved savanna. By contrast, only eight species were recorded in the eucalyptus plantation and none of them were exclusive to this vegetation. However, the landscape patchwork formed by plantations and savanna was more diverse and contained 19 species of mammals, highlighting the potential importance of remnant savanna vegetation. The maintenance of remnants of savanna habitat may thus be essential for ensuring the conservation of mammals in the anthropogenic landscape of this region. It will also be important to include as many different subtypes of native savanna vegetation as possible and to consider the connectivity between habitats.

Proechimys (Rodentia, Echimyidae): characterization and taxonomic considerations of a form with a very low diploid number and a multiple sex chromosome system

BackgroundProechimys is the most diverse genus in family Echimyidae, comprising 25 species (two of which are polytypic) and 39 taxa. Despite the numerous forms of this rodent and their abundance in nature, there are many taxonomic problems due to phenotypic similarities within the genus and high intraspecific variation. Extensive karyotypic variation has been noted, however, with diploid numbers (2n) ranging from 14 to 62 chromosomes. Some heteromorphism can be found, and 57 different karyotypes have been described to date.ResultsIn the present work, we describe a cytotype with a very low 2n. Specimens of Proechimys cf. longicaudatus were collected from two different places in northern Mato Grosso state, Brazil (12°54″S, 52°22″W and 9°51′17″S, 58°14′53″W). The females and males had 16 and 17 chromosomes, respectively; all chromosomes were acrocentric, with the exception of the X chromosome, which was bi-armed. The sex chromosome system was found to be XY1Y2, originating from a Robertsonian rearrangement involving the X and a large acrocentric autosome. Females had two Neo-X chromosomes, and males had one Neo-X and two Y chromosomes. NOR staining was found in the interstitial region of one autosomal pair.ConclusionsComparison of this karyotype with those described in the literature revealed that Proechimys with similar karyotypes had previously been collected from nearby localities. We therefore suggest that this Proechimys belongs to a different taxon, and is either a new species or one that requires reassessment.

Diversidade de mamíferos de médio e grande porte da região do rio Urucu, Amazonas, Brasil

Between April 2008 and May 2009, studies on the species richness, composition and relative abundance of the medium and large sized mammals were carried out in the Urucu basin (Brazilian Amazon). The survey was conducted using line transect sampling method, active search for signs and camera-traps. A total of 41 species of 17 families and eight orders were recorded. Primates was the group with the highest species richness in sympatry (13 species), followed by carnivores (11 species). Primates, Perissodactyla, Artiodactyla and Rodentia were the most abundant groups. The high diversity of medium and large sized mammals presented here indicates the importance of the region for mammals conservation in Amazonia.

Extensive Chromosomal Reorganization in the Evolution of New World Muroid Rodents (Cricetidae, Sigmodontinae): Searching for Ancestral Phylogenetic Traits

Sigmodontinae rodents show great diversity and complexity in morphology and ecology. This diversity is accompanied by extensive chromosome variation challenging attempts to reconstruct their ancestral genome. The species Hylaeamys megacephalus–HME (Oryzomyini, 2n = 54), Necromys lasiurus—NLA (Akodontini, 2n = 34) and Akodon sp.–ASP (Akodontini, 2n = 10) have extreme diploid numbers that make it difficult to understand the rearrangements that are responsible for such differences. In this study we analyzed these changes using whole chromosome probes of HME in cross-species painting of NLA and ASP to construct chromosome homology maps that reveal the rearrangements between species. We include data from the literature for other Sigmodontinae previously studied with probes from HME and Mus musculus (MMU) probes. We also use the HME probes on MMU chromosomes for the comparative analysis of NLA with other species already mapped by MMU probes. Our results show that NLA and ASP have highly rearranged karyotypes when compared to HME. Eleven HME syntenic blocks are shared among the species studied here. Four syntenies may be ancestral to Akodontini (HME2/18, 3/25, 18/25 and 4/11/16) and eight to Sigmodontinae (HME26, 1/12, 6/21, 7/9, 5/17, 11/16, 20/13 and 19/14/19). Using MMU data we identified six associations shared among rodents from seven subfamilies, where MMU3/18 and MMU8/13 are phylogenetic signatures of Sigmodontinae. We suggest that the associations MMU2entire, MMU6proximal/12entire, MMU3/18, MMU8/13, MMU1/17, MMU10/17, MMU12/17, MMU5/16, MMU5/6 and MMU7/19 are part of the ancestral Sigmodontinae genome.

Cryptic Species in Proechimys goeldii (Rodentia, Echimyidae)? A Case of Molecular and Chromosomal Differentiation in Allopatric Populations

The spiny rats of the genus Proechimys have a wide distribution in the Amazon, covering all areas of endemism of this region. We analyzed the karyotype and cytochrome b (Cyt b) sequences in Proechimys goeldii from 6 localities representing 3 interfluves of the eastern Amazon. A clear separation of P. goeldii into 2 monophyletic clades was observed, both chromosomally and based on Cyt b sequences: cytotype A (2n = 26♀/27♂, NF = 42) for samples from the Tapajos-Xingu interfluve and cytotype B (2n = 24♀/25♂, NF = 42) for samples from the Xingu-Tocantins interfluve and east of the Tocantins River. The karyotypes differ in a pericentric inversion and a centric fusion/fission and an average nucleotide divergence of 6.1%, suggesting cryptic species. Meiotic analysis confirmed the presence of a XX/XY1Y2 multiple sex chromosome determination system for both karyotypes. The karyotypes also vary from the literature (2n = 24, NF = 42, XX/XY). The autosome translocated to the X chromosome is different both in size and morphology to P. cf. longicaudatus, which also has a multiple sex chromosome determination system (2n = 14♀/15♀♂/16♀/17♂, NF = 14). The Xingu River is a barrier that separates populations of P. goeldii, thus maintaining their allopatric nature and providing an explanation for the molecular and cytogenetic patterns observed for the Xingu River but not the Tocantins River.

Edge effects and the impact of wildfires on populations of small non-volant mammals in the forest-savanna transition zone in Southern Amazonia

O efeito de borda e do fogo sobre a comunidade de pequenos mamiferos nao-voadores foi investigada em uma area de transicao entre Cerrado e Floresta em uma area de matriz de soja na Amazonia Oriental. Os individuos foram coletados em 24 transectos, dos quais 16 foram distribuidos em area sem efeito do fogo e oito distribuidos com efeito do fogo. Um total de 11 especies foi registrado, incluindo seis roedores e cinco marsupiais. A especie Hylaeamys megacephalus foi a mais abundante em areas sem efeito do fogo. A abundância e riqueza de pequenos mamiferos nao-voadores apresentaram uma diminuicao em areas queimadas, entretanto o efeito do fogo parece mascarar o efeito de borda nestas mesmas areas. Em relacao ao efeito de borda, sem nenhum efeito de fogo, a relacao entre a abundância de pequenos mamiferos nao-voadores com a distância da borda foi positiva. A relacao entre a diversidade de pequenos mamiferos e efeito de borda pode ser ligada a vegetacao matriz e caracteristicas ecologicas de cada especie.

Environmental Assessment and Aquatic Biodiversity Conservation of Amazonian Savannas, Marajó Island, Brazil

Marajo Island is located in the mouth of the Amazon River, the World’s largest river, at its interface with the Atlantic Ocean (Goulding et al., 2003). Marajo is the World’s largest riverine island (Cruz, 1987), with a total area of approximately fifty thousand square kilometers (Fig. 1). In addition to the Amazon, the island is also influenced by the Tocantins River and other small rivers of the south (Barthem & Schwassmann, 1994; UNEP, 2004). The island is surrounded by sandy-clayey beaches, and encompasses a hydrographic system (rivers, channels, and creeks) which both drains and floods the terra firme forest and varzeas (swamps) (Marques-Aguiar et al., 2002). In addition to these forest ecosystems, the island’s lakes, lagoons, beaches, rivers, and mangroves contribute to its diversity of habitats and organisms (Marques-Aguiar et al., 2002; Montag et al., 2009; Almeida et al., 2009). This diversity of habitats influences the richness of the region’s fauna, including its fish, and plays an important role in habitat preferences and use (Lowe-McConnell, 1999; Carrier et al., 2004). Most of these environments are heavily influenced by the inundation cycle of the estuarine region, which Junk (1997) characterizes as a polymodal cycle of low amplitude, but highly predictable flood pulses, influenced primarily by the local tides. The climate of Marajo Island can be characterized by two categories of the Koppen classification system – Af (humid tropical, with mean precipitation in the driest month at least 60 mm) and Am, tropical monsoon, with excessive rainfall between February and May. During this period, two-thirds of the island are completely flooded (Cardoso & Pereira, 2002; Lima et al., 2005; Fig. 1). Annual precipitation on Marajo Island ranges between 2500 mm and 4000 mm, with a mean temperature of around 27oC, and relative humidity of 81% to 94%. Rainfall is distributed in two distinct periods, with a marked rainy season between January and June, and a dry season, between September and November. Despite this rigorous hydrological regime, the vegetation covering the part of the island that is flooded annually is referred to as a savanna (or flooded grassland; Fig. 2), which is known for the diversity and abundance of its fishery resources (Barthem & Fabre, 2003; Montag et al., 2009; Schaan, 2010). While the term savanna is more associated with specific floristic characteristics, comparable with those of the savannas of central Brazil (Eiten, 1972; Ratter et

Anatomical and histological characteristics of teeth in agouti (Dasyprocta prymnolopha Wagler, 1831)

The agouti species Dasyprocta prymnolopha (D. prymnolopha) is a medium-sized rodent, diurnal, and characteristic of northeastern Brazil, south of the Amazon. Several studies have been made on these rodents. However, there is a lack of analysis of masticatory system, in particular morphology of the teeth. Thus, this research seeks to describe anatomical and histological aspects of the agouti teeth. For this purpose, we used adult agouti, in which measurements and descriptions of teeth and dental tissues were made. It was observed that the dental arch of D. prymnolopha comprises of twenty teeth, evenly distributed in the upper and lower arch, being inferior teeth larger than their corresponding higher. The incisors are larger, and between the posterior premolars and molars, there is a gradual increase in length in the anterior-posterior arch. In microscopic examination, a prismatic appearance was observed consisting of enamel prisms arranged in different directions, behind the enamel and dentin with standard tubular dentinal tubules with variable diameter and far between, also showing a sinuous path from the inner portion to the junction with more superficial enamel. Morphological analysis of dental tissues showed that an enamel with structural organization adapted to the act of chewing and high impact dentin compatible with standard tubular function resilience and mechanical damping of masticatory forces, as found in larger animals, confirming the understanding of eating habits that define much of its ecological functions within the ecosystem they inhabit.

Chromosomal diversity and molecular divergence among three undescribed species of Neacomys (Rodentia, Sigmodontinae) separated by Amazonian rivers

The Neacomys genus (Rodentia, Sigmodontinae) is distributed in the Amazon region, with some species limited to a single endemic area, while others may occur more widely. The number of species within the genus and their geographical boundaries are not known accurately, due to their high genetic diversity and difficulties in taxonomic identification. In this work we collected Neacomys specimens from both banks of the Tapajós River in eastern Amazon, and studied them using chromosome painting with whole chromosome probes of Hylaeamys megacephalus (HME; Rodentia, Sigmodontinae), and molecular analysis using haplotypes of mitochondrial genes COI and Cytb. Chromosome painting shows that Neacomys sp. A (NSP-A, 2n = 58/FN = 68) and Neacomys sp. B (NSP-B, 2n = 54/FN = 66) differ by 11 fusion/fission events, one translocation, four pericentric inversions and four heterochromatin amplification events. Using haplotypes of the concatenated mitochondrial genes COI and Cyt b, Neacomys sp. (2n = 58/FN = 64 and 70) shows a mean divergence of 6.2% for Neacomys sp. A and 9.1% for Neacomys sp. B, while Neacomys sp. A and Neacomys sp. B presents a medium nucleotide divergence of 7.4%. Comparisons were made with other published Neacomys data. The Tapajós and Xingu Rivers act as geographic barriers that define the distribution of these Neacomys species. Furthermore, our HME probes reveal four synapomorphies for the Neacomys genus (associations HME 20/[13,22]/4, 6a/21, [9,10]/7b/[9,10] and 12/[16,17]) and demonstrate ancestral traits of the Oryzomyini tribe (HME 8a and 8b, 18 and 25) and Sigmodontinae subfamily (HME 15 and 24), which can be used as taxonomic markers for these groups.

Odocoileus virginianus , Zimmermann, 1780 (Mammalia: Cervidae): confirmed records and distribution extension in the northern Brazilian Amazon

We present details of five new field records of Odocoileus virginianus from the northern Brazilian Amazon, extending its known range from Suriname to the Brazilian state of Para. We also document four sight records and four records based on specimens held in collections of white-tailed deer distribution from the states of Amapa and Roraima, reinforcing this inferred distribution. Confirmation of the occurrence of O. virginianus in the Brazilian Amazon is important for its conservation, since it is an important game species for traditional human populations and requires population-level management.