The western Amazon is one of the world's last high-biodiversity wilderness areas, characterized by extraordinary species richness and large tracts of roadless humid tropical forest. It is also home to an active hydrocarbon (oil and gas) sector, characterized by operations in extremely remote areas that require new access routes. Here, we present the first integrated analysis of the hydrocarbon sector and its associated road-building in the western Amazon. Specifically, we document the (a) current panorama, including location and development status of all oil and gas discoveries, of the sector, and (b) current and future scenario of access (i.e. access road versus roadless access) to discoveries. We present an updated 2014 western Amazon hydrocarbon map illustrating that oil and gas blocks now cover 733 414 km 2 , an area much larger than the US state of Texas, and have been expanding since the last assessment in 2008. In terms of access, we documented 11 examples of the access road model and six examples of roadless access across the region. Finally, we documented 35 confirmed and/or suspected untapped hydrocarbon discoveries across the western Amazon. In the Discussion, we argue that if these reserves must be developed, use of the offshore inland model-a method that strategically avoids the construction of access roads-is crucial to minimizing ecological impacts in one of the most globally important conservation regions.

Army ants (Formicidae: Ecitoninae) are top predators in neotropical forests. Army ant raids support a community of diverse organisms, including birds that attend the raids to collect prey. While elevation and forest fragmentation influence army ant and insectivorous bird communities, their effects on the interaction between army ants and bird species is unknown. We studied the size and species composition of bird flocks attending army ant swarms in forest fragments and continuous forest across an elevational gradient (1100–1680 m asl) in a neotropical montane region (Monteverde, Costa Rica). We observed a total of 41 bird species attending army ant swarms. Neither the number of birds, nor the total body mass of birds, nor the number of bird species in attending bird flocks was related to elevation. However, we found a higher bird species richness, larger flock size and greater total body mass of birds attending army ant swarms in continuous forest. Continuous and fragmented forest shared many attending bird species in common, but there was elevational segregation of attending bird species. Some montane endemic birds, and neotropical migrants, attend swarms regularly and use army ant raids as a food source.

Estimating species richness in large biomes is a central challenge in ecology and conservation biology. However, accurate census data is often available only from small discrete plots distributed within the biome. Using tree species richness data collected from 48 plots (0.25 ha each) widely distributed through 60 000 km 2 in the rainforests of the Western Ghats of southern India, we test the application of a proposed method for estimating species richness at large scales from measured species commonalities between pairs of censused plots. We show that the method allows extrapolation of species richness from a scale of 0.25 ha plots to that of the entire biome, or 10 5 km 2 . R. Krishnamani

We used a standard sampling protocol to measure elevational patterns of species richness and abundance of eusocial paper wasps (Hymenoptera: Vespidae) in Costa Rica. The sample transect of six sites spanned approximately 2000 m in elevation from lowland to montane forest. Species accumulation curves and species richness estimates both document a low elevation peak in paper wasp species richness at 50 and 300 m asl, with a decline in species richness at higher elevations. Comparison of species composition among elevations revealed strong species turnover from a rich lowland fauna to a depauperate, but distinct, montane fauna. We also observed a general trend toward a greater abundance of paper wasps at higher elevations, a pattern not usually observed in eusocial insects. Army ant species that prey on paper wasps declined in abundance with elevation across the sample transect, a pattern that has been observed at other sites. We discuss the possibility that elevational changes in predation pressure affect variation in paper wasp abundance and species richness. Eusocial paper wasp species employ one of two modes of colony founding, independent and swarm founding. We found that the total abundance of individual swarm‐founding wasps was higher at all elevations than the abundance of independent‐founding wasps, supporting previous suggestions that Neotropical swarm founders are more successful ecologically.

1. The density (rate of encountering foraging raids) and species richness of army ants (Formicidae: Ecitoninae, and behaviourally convergent Ponerinae) was measured in montane tropical forest. Above-ground and subterranean army ant raids were sampled using standard protocols at four sites across an elevational gradient (1200 -1650 m above mean sea level) in and near cloud forest in the area of Monteverde, Costa Rica.2. Mean ambient temperature differed among sites, and decreased with elevation. For the above-ground foraging army ant species, raid rates also declined with elevation. Surface army ant raid rates, however, were not affected by day to day weather variation within sites (temperature, cloud cover, or precipitation).3. For the underground foraging army ant species, raid rates did not vary directionally with elevation, and subterranean raid rates were not affected by day to day weather variation within sites.4. Army ant species richness was not directionally related to elevation, and species sharing among sites was generally high. 5. Army ant community structure changes with elevation in Neotropical montane forest, and the results suggest that the strongest effects are of temperature regimes on the density of raids. These findings provide a baseline against which to detect changes in army ant communities that may accompany directional climate change in tropical cloud forests.