RESUMEN
Tropical rainforests support the greatest diversity of small mammals in the world, yet we have little understanding about the mechanisms that promote the coexistence of species. Diet partitioning can favor coexistence by lessening competition, and interspecific differences in body size and habitat use are usually proposed to be associated with trophic divergence. However, the use of classic dietary methods (e.g. stomach contents) is challenging in small mammals, particularly in community-level studies, thus we used stable isotopes (δ13C and δ15N) to infer about trophic niche. We investigated i) how trophic niche is partitioned among rodent and marsupial species in three Atlantic forest sites and ii) if interspecific body size and locomotor habit inequalities can constitute mechanisms underlying the isotopic niche partitioning. We found that rodents occupied a broad isotopic niche space with species distributed in different trophic levels and relying on diverse basal carbon sources (C3 and C4 plants). Surprisingly, on the other hand, marsupials showed a narrow isotopic niche, both in δ13C and δ15N dimensions, which is partially overlapped with rodents, contradicting their description as omnivores and generalists proposed classic dietary studies. Although body mass differences did not explained the divergence in isotopic values among species, groups of species with different locomotor habit presented clear differences in the position of the isotopic niche space, indicating that the use of different forest strata can favor trophic niche partitioning in small mammals communities. We suggest that anthropogenic impacts, such as habitat modification (logging, harvesting), can simplify the vertical structure of ecosystems and collapse the diversity of basal resources, which might affect negatively small mammals communities in Atlantic forests.
Asunto(s)
Ecosistema , Isótopos , Marsupiales , Roedores , Animales , Brasil , BosquesRESUMEN
Atlantic Forest, in the eastern coast of Brazil, is a hotspot of biodiversity of mammals, and Parque Estadual da Serra do Mar (PESM) is the largest continuous area of this biome. Here, we characterized the karyotype composition of the small mammals from Santa Virgínia, a region in the northern part of PESM. Specimens were collected from July 2008 to September 2009. We identified 17 species (13 rodents and 4 marsupials) from which 7 exhibited species-specific karyotypes, illustrating the importance of karyotype information in cytotaxonomy. We report for first time the karyotype of Monodelphis scalops (Thomas, 1888) and two new records for PESM: Akodon montensis Thomas, 1913 and Brucepattersonius soricinus Hershkovitz, 1998. Cytogenetic polymorphisms were detected for some species trapped in the area. Our results show the importance of Santa Virgínia / PESM in addressing studies for the conservation of small mammal wildlife in the Atlantic Forest.
RESUMEN
This study presents data on the composition and species richness of non-flying mammals in the northern part of the Parque Estadual da Serra do Mar, called Núcleo Santa Virgínia (NSV - around 17000 hectares of Atlantic Forest), São Paulo state, southeastern Brazil. The species list was based on ca. 660 km of line-transects, 25512 hours of cameras traps, 7740 trap.nights for small mammals, and 394 track-station.days, as well as occasional records and registers from local people (period 2002 to 2009). Based on these complementary methods, a total of 58 species were recorded from the 85-104 possible. Eighteen taxa are listed in the Brazilian endangered species list, 29 in the state list. The high species richness of non-volant mammals and the presence of threatened species show the importance of NSV for the conservation of Atlantic Forest mammals.
Este estudo apresenta dados de composição e riqueza de espécies de mamíferos não voadores da porção norte do Parque Estadual da Serra do Mar, que corresponde è região do núcleo Santa Virgínia (NSV - cerca de 17.000 hectares de Floresta Atlântica), estado de São Paulo, sudeste do Brasil. A listagem de espécies foi elaborada durante o período de 2002 a 2009, por meio de ca. 660 km de transecções lineares, 25.512 horas de armadilha fotográfica, 394 armadilhas-de-pegada.dia, registros ocasionais e relatos de moradores da região (entrevistas) para mamíferos de médio e grande porte, e 7.740 armadilhas.noite para pequenos mamíferos. Foram registradas 58 espécies de 85-104 de possível ocorrência dada suas potenciais distribuições. Dezoito espécies fazem parte da lista nacional da fauna ameaçada de extinção e 29 da lista estadual. A elevada riqueza de mamíferos não voadores com a presença de várias espécies ameaçadas, indica a importância do NSV para conservação da mastofauna regional.