Potential dispersal of Cecropia hololeuca by the common opossum (Didelphis aurita) in Atlantic forest, southeastern Brazil

Plusieurs auteurs ont reconnu le rôle des vertébrés comme disperseurs de graines de Cecropia. Nous avons comparé sous des traitements différents (lumière et absence de lumière) les taux de germination de graines de Cecropia hololeuca provenants des fèces de Didelphis aurita à ceux de graines issues de fruits prélevés sur des arbres. En outre, les graines des arbres ont été séparées en trois goupes pour des tests de germination : fruits frais, 15 jours après collecte et 30 jours après collecte. La germination sous lumière a eu plus de succès que sans lumière, pour tous les groupes (fruits frais, 15 jours après collecte et 30 jours après collecte, et fèces). Le taux de germination des graines provenant des fèces ont été plus proches de ceux de 30 jours après collecte que des autres groupes. Ces résultats suggèrent que D. aurita se nourrit au sol de fruits de C. hololeuca. La possibilité que D. aurita disperse les graines dans des zones au-delà des arbres parentaux, jointe au fait que les taux de germination similaires entre graines issues des fèces et graines provenant de fruits récoltés impliquent que D. aurita serait un disperseur potentiel de C. hololeuca

CARACTERÍSTICAS DETERMINANTES DO RISCO DE EXTINÇÃO GLOBAL DE MAMÍFEROS

CHARACTERISTICS DETERMINANTS OF GLOBAL EXTINCTION RISK OF MAMMALS. About one-quarter of all mammals are in danger of extinction and is essential to the Conservation Biology identifying the factors that predict extinction risk. Some studies have made considerable efforts to recognize the relevant characteristics associated to vulnerability of extinction. In order to investigate if there is a consensus about what characteristics were more related to the extinction risk of mammals, we reviewed all the literature that found attributes of species correlated with vulnerability degree. Our results show that species of mammals tend to have a higher risk of extinction if they occupy small geographical range, have large body size and exhibit low reproductive rate, however they may differ according to the taxon and region studied. For example, carnivores shown to be greatly affected by low fecundity, while the same is not observed for primates. Furthermore, larger species are at higher risk only in tropical regions. The interaction between biological traits and anthropogenic threats increase understanding of the processes determining extinction risk. Keywords: Conservation; endangered species; fecundity; body size; geographical range.CARACTERISTICAS DETERMINANTES DEL RIESGO DE EXTINCIÓN GLOBAL DE MAMIFEROS. Aproximadamente un cuarto de todas las especies de mamíferos poseen algún grado de amenaza, y entender cuáles son los factores que determinan el riesgo de extinción de estas especies es uno de los mayores desafíos para la Biología de la Conservación. Algunos estudios han hecho considerables esfuerzos para reconocer las características relevantes asociadas al grado de vulnerabilidad. Para investigar si existe un consenso general sobre que características se relacionan más con el riesgo de extinción de los mamíferos, analizamos toda la literatura que encontró atributos de la especie correlacionados con el grado de vulnerabilidad. Nuestros resultados muestran que las especies de mamíferos tienden a tener un alto riesgo deextinción si ocupan un rango geográfico pequeño, tienen un gran tamaño corporal y baja tasa reproductiva, sin embargo, ellas pueden diferenciarse según el taxón y la región estudiada. Por ejemplo, los carnívoros mostraron estar más afectados por la baja fecundidad, mientras que en primates no se observó lo mismo. Además, las especies más grandes tienen el riesgo más alto solamente en regiones tropicales. Finalmente, la interacción entre los rasgos biológicos y los disturbios antrópicos aumenta el entendimiento de los procesosque determinan el riesgo de extinción. Palabras claves: Conservación; especies amenazadas; fecundidad; tamaño corporal; rango de distribución.Aproximadamente um quarto de todas as espécies de mamíferos possui algum grau de ameaça, e entender que fatores determinam o risco de extinção destas espécies é um dos maiores desafios da Biologia da Conservação. Muitos trabalhos tentam responder esta questão procurando as associações existentes entre as características biológicas e ecológicas das espécies com o seu grau de vulnerabilidade. Esse estudo se propôs a investigar se há um consenso na literatura sobre quais destas características estariam mais relacionadas com o risco de extinção de mamíferos. Os resultados mostraram que tamanho corporal, fecundidade e tamanho de distribuição são as principais características responsáveis pelo risco de extinção dos mamíferos, mas que estas podem diferir de acordo com o táxon e região estudados. Carnívoros mostraram ser muito afetados pela baixa fecundidade, enquanto o mesmo não é observado para primatas. Além disso, tamanho corporal parece ser uma característica importante somente nos trópicos. E finalmente, a interação destas características com fatores ecológicos e distúrbios antrópicos nos proporciona uma compreensão mais completa do assunto. 

Effects of Brazil's political crisis on the science needed for biodiversity conservation

The effects of Brazil’s political crisis on science funding necessary for biodiversity conservation are likely to be global. Brazil is not only the world’s most biodiverse nation, it is responsible for the greater part of the Amazon forest, which regulates the climate and provides rain to much of southern South America. Brazil was a world leader in satellite monitoring of land-use change, in-situ biodiversity monitoring, reduction in tropical-forest deforestation, protection of indigenous lands, and a model for other developing nations. Coordinated public responses will be necessary to prevent special-interest groups from using the political crisis to weaken science funding, environmental legislation and law enforcement. Keywords: Brazil, biodiversity, climate change, governance, fundin

The role of competition in structuring primate communities under different productivity regimes in the Amazon

The factors responsible for the formation of Amazonian primate communities are not well understood. Here we investigated the influence of interspecific competition in the assembly of these communities, specifically whether they follow an assembly rule known as "favored states". According to this rule, interspecific competition influences final species composition, resulting in functional groups that are equally represented in the community.We compiled presence-absence data for primate species at 39 Amazonian sites in Brazil, contrasting two regions with distinct productivity regimes: the eutrophic Juruá River basin and the oligotrophic Negro River basin. We tested two hypotheses: that interspecific competition is a mechanism that influences the structure of Amazonian primate communities, and that competition has had a greater influence on the structure of primate communities in regions with low productivity, where resources are more limited. We used null models to test the statistical significance of the results, and found a non-random pattern compatible with the favored states rule in the two regions. Our findings suggest that interspecific competition is an important force driving primate community assembly regardless of productivity regimes

Effectiveness of a reserve network for the conservation of the endemic marsupial Micoureus travassosi in Atlantic Forest remnants in southeastern Brazil

Abstract. Habitat loss and fragmentation are serious threats to biodiversity conservation in the Atlantic Forest. A network of protected reserves is essential to the protection of native fauna and flora. However, internal and external factors may threaten the preservation of biota, thus population viability analyses (PVA) are important tools in reserve design and management planning. A PVA was carried out, using the computer package VORTEX, to assess the effectiveness of the reserve network of Rio de Janeiro State in Brazil in retaining viable populations of the endemic marsupial Micoureus travassosi. The PVA takes into account demographic, genetic and environmental stochastic events and catastrophes (fire). Rio de Janeiro state has 31 reserves, and 20 of those were considered to retain viable populations for 100 years, whereas eight were predicted to suffer from genetic decay, two from both genetic decay and demographic stochasticity, and one of them probably has an extinct population. The minimum area of suitable habitat needed to maintain a minimum viable population of M. travassosi is estimated at 3600 ha. Sensitivity analysis was run for mortality, sex ratio, percentage of reproductive females, inbreeding depression and probability of catastrophes, and suggests that inbreeding depression is important in small population sizes, whereas the effects of catastrophes were significant only for large populations. Although the model indicates that some populations will suffer from demographic and/or genetic stochasticity, the reserve network of Rio de Janeiro state will likely keep M. travassosi's populations for the next 100 years

Potential dispersal of Cecropia hololeuca by the Common Opossum (Didelphis aurita) in Atlantic forest, south-eastern Brazil

Several authors have recognized the role of vertebrates as seed disperser of Cecropia. Germination rates of Cecropia hololeuca from scats of Didelphis aurita and from trees were tested in different treatments (light and dark). In addition, seeds from trees were separated in three groups for germination tests : fresh-fruit, 15 days after collection, 30 days after collection. Seed germination under light were more successful than in dark for all groups (fresh-fruit, 15 days after, 30 days after, and from scats). Germination rate of seeds from scats were closer to germination rates of the 30 days after collection group than other groups. These results insinuate that D. aurita feeds on fruit of C. hololeuca on the ground. The possibility that D. aurita disperses seeds to areas beyond parent trees, plus the similar germination rates of seeds from scats with seeds from fruiting trees imply that D. aurita is a potential disperser of C. hololeuca.Plusieurs auteurs ont reconnu le rôle des vertébrés comme disperseurs de graines de Cecropia. Nous avons comparé sous des traitements différents (lumière et absence de lumière) les taux de germination de graines de Cecropia hololeuca provenants des fèces de Didelphis aurita à ceux de graines issues de fruits prélevés sur des arbres. En outre, les graines des arbres ont été séparées en trois groupes pour des tests de germination : fruits frais, 15 jours après collecte et 30 jours après collecte. La germination sous lumière a eu plus de succès que sans lumière, pour tous les groupes (fruits frais, 15 jours après collecte et 30 jours après collecte, et fèces). Le taux de germination des graines provenant des fèces ont été plus proches de ceux de 30 jours après collecte que des autres groupes. Ces résultats suggèrent que D. aurita se nourrit au sol de fruits de C. hololeuca. La possibilité que D. aurita disperse les graines dans des zones au-delà des arbres parentaux, jointe au fait que les taux de germination similaires entre graines issues des fèces et graines provenant de fruits récoltés impliquent que D. aurita serait un disperseur potentiel de C. hololeuca.Grelle Carlos Eduardo de Viveiros, Garcia Queila S. Potential dispersal of Cecropia hololeuca by the Common Opossum (Didelphis aurita) in Atlantic forest, south-eastern Brazil. In: Revue d'Écologie (La Terre et La Vie), tome 54, n°4, 1999. pp. 327-332