No abstract

The ant fauna of state of Acre, Brazilian Amazon, is poorly known. The aim of this study was to compile the species sampled in different areas in the State of Acre. An inventory was carried out in pristine forest in the municipality of Xapuri. This list was complemented with the information of a previous inventory carried out in a forest fragment in the municipality of Senador Guiomard and with a list of species deposited at the Entomological Collection of National Institute of Amazonian Research– INPA. The resulting list covered 268 species distributed in 52 genera and nine subfamilies, and records 23 species and four morphospecies for the first time in the state of Acre. Due to the large environmental heterogeneity, future inventories will be crucial to properly describe and understand ant species distribution patterns in southwestern Amazon.

Floodplain areas comprise some 30% of the area in the Amazon, but are currently under severe anthropogenic threat. Across the Amazon Basin, forest-dwelling non-volant mammals play crucial roles in maintaining the integrity of forest functionality, yet have been poorly studied in fluvial island forests. Mammal assemblages may be affected by edaphic characteristics that operate indirectly via food nutritional quality, by patch attributes, and/or can be modulated by anthropogenic disturbances. Here, we conducted systematic and quantitative mammal surveys across fluvial islands of an Amazonian archipelago, to assess the influence of edaphic factors (soil fertility), island attributes (island area and degree of isolation) and anthropogenic characteristics (distance from human settlement and logging) on the patterns of mammal species composition and richness. On 28 islands, we conducted spoor surveys and deployed 49 camera traps (total effort of 2940 camera trap-days). Subsequently, we performed multiple regression analysis to investigate the influence of environmental and anthropogenic predictors on mammal species richness, while dbRDA (distance-based redundancy analysis) was used for species composition. We found that mammal species richness was positively correlated with soil fertility, and in combination with anthropogenic characteristics, both variables affected the species assemblage composition. In particular, smaller species were found across a variety of levels of soil fertility and anthropogenic disturbances, while larger mammals were mostly recorded at sites with higher soil fertility and low levels of anthropogenic disturbances. Understanding the contribution of environmental and anthropogenic characteristics to the observed mammalian species richness and assemblage composition patterns will help optimise management and conservation efforts on Amazonian fluvial islands. In particular, we suggest enforcing hunting and logging restrictions within fluvial islands through surveillance activities, especially in more fertile islands.

Abstract1. Arthropod diversity and non-flying arthropod food web are strongly influenced by habitat components related to plant architecture and habitat structural complexity. However, we still poorly understand the relationship between arthropod diversity and the vegetation structure at different spatial scales. Here, we examined how harvestmen assemblages are distributed across six local scale habitats (trees, dead trunks, palms, bushes, herbs and litter), and along three proxies of vegetation structure (number of palms, number of trees and litter depth) at mesoscale.2. We collected harvestmen using cryptic manual search in 30 permanent plots of 250 m at Reserva Ducke, Amazonas, Brazil. The 30 plots cover approximately 25 km2 of upland forests. At a local scale, harvestmen were most diverse and abundant on trees. The likely preference of trees by harvestmen may be related to the variety of local microhabitats offered by large trees. However, despite the strong link between number of harvestman species and individuals with large trees, only harvestmen assemblages composition were related with number of trees and with number of palms, at mesoscale.3. Harvestman richness and abundance were not related with any vegetation structure predictor at mesoscale. Therefore, areas of upland forest in the central Amazon with large trees and palms do not harbor more harvestman species nor individuals, but are suitable to maintain different harvestmen assemblages.

No abstract

Invertebrates can be sampled using any of several well-established, rapid and cost-effective methods for documenting species richness and composition. Despite their many differences, different orders of arachnids have been often sampled together in various studies. Active nocturnal search has been long considered the most efficient method for sampling spiders and harvestmen in tropical forests. We compared the number of species and composition of spiders and harvestmen simultaneously sampled using three sampling methods: beating tray, active nocturnal search and Winkler traps at areas along the Urucu River, Coari, Amazonas. We found that a reasonable inventorying of harvestmen can be accomplished solely by nocturnal search, whereas the beating tray and Winkler approaches are redundant. For spiders, both the nocturnal and beating tray methods were complementary and are needed to provide a more complete picture of spider assemblages. An inventory based solely on nocturnal search saves 75% of the survey costs for harvestmen assemblages and 46% for spider assemblages. Based on our findings we propose that different taxonomic groups (e.g. harvestmen and spiders) should be sampled separately in tropical forests, especially for monitoring purposes, and different sets of methods should be combined for each according to their most efficient and best cost-benefit performance.

No abstract

O objetivo deste trabalho foi avaliar a composição, riqueza e abundância de formigas (Hymenoptera: Formicidae) em ambientes de savana e sistemas associados aproveitando os gradientes de uso (natural; antrópico) e estrutura da vegetação (florestal; não-florestal). Os ecossistemas avaliados foram (i) mosaico de savana parque-campo sujo (natural; não-florestal), (ii) mata galeria em ambiente de savana (natural; florestal), (iii) capoeira derivada de contato floresta-savana (antropizado; florestal) e (iv) silvicultura de Acacia mangium Willd. derivada de savana parque (antropizado; florestal). Foram utilizados dois métodos de coleta, isca de sardinha e armadilhas de queda (pitfall traps). Cada ecossistema foi amostrado de duas a quatro vezes entre os meses de setembro e dezembro de 2007. Cada rodada de coleta consistiu de 25 unidades amostrais de cada método distribuídas em cinco transectos de 100 m, distanciados 40 m entre si abrangendo uma área de 100 m2. Somados os dois métodos de coleta, foram identificadas 77 espécies ou morfo-espécies de formigas pertencentes a sete subfamílias (25.408 indivíduos). A monocultura de A. mangium apresentou 49 espécies, mata galeria 46, capoeira 44 e savana 25. Os dois gêneros de maior ocorrência foram Crematogaster (60,4% dos indivíduos) e Pheidole (24,8%). Não foi encontrado nenhum padrão de composição das espécies evidente pela análise de MDS (Escalonamento Multidimensional Não-métrico). Existe uma fraca tendência de agrupamento das amostras da mata galeria, porém as amostras coletadas na savana, normalmente consideradas áreas mais homogêneas, apresentaram a maior diferença de composição.