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., et al. 2012. Positive relationships between association strength and phenotypic similarity characterize the assembly of mixed-species bird flocks worldwide. American Naturalist 180: 777-90. AuthorsHari Sridhar, Umesh Srinivasan, Robert A. Askins, Julio Cesar Canales-Delgadillo, Chao-Chieh Chen Submitted February 10, 2012; Accepted August 1, 2012; Electronically published MONTH? xx, 2012 Online enhancement: appendix. Dryad data: http://dx.doi.org/10.5061/dryad.th198.abstract: Competition theory predicts that local communities should consist of species that are more dissimilar than expected by chance. We find a strikingly different pattern in a multicontinent data set (55 presence-absence matrixes from 24 locations) on the composition of mixed-species bird flocks, which are important subunits of local bird communities the world over. By using null models and randomization tests followed by meta-analysis, we find the association strengths of species in flocks to be strongly related to similarity in body size and foraging behavior and higher for congeneric compared with noncongeneric species pairs. Given the local spatial scales of our individual analyses, differences in the habitat preferences of species are unlikely to have caused these association patterns; the patterns observed are most likely the outcome of species interactions. Extending group-living and social-information-use theory to a heterospecific context, we discuss potential behavioral mechanisms that lead to positive interactions among similar species in flocks, as well as ways in which competition costs are reduced. Our findings highlight the need to consider positive interactions along with competition when seeking to explain community assembly.

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Orchid bees (Apidae, Euglossini) are important pollinators in the Amazon forest. In eastern Brazilian Amazon, secondary forest and pastures are being replaced by oil palm plantations. Here, we tested the role of forest reserves and riparian corridors in maintaining orchid bees. We sampled bees in three different soil-type uses, comparing richness, abundance, and assemblage composition. Estimated richness was lowest in palm plantations than in forest reserves and riparian corridors on diversity of orchid bees. Riparian corridors had the highest abundance, followed by reserves, and oil palm plantations. Bee assemblage also varied with land cover, with the reserves having the most distinct composition. We also identified indicator bees for primary forest. Our results demonstrate riparian corridors and forest reserves can maintain orchid bees in oil palm landscapes.

Interactions between species in groups are often ignored in studies of the effects of anthropogenic change on species' persistence, and yet, given their global ubiquity, mixed‐species groups have the potential to be models for community ecology. In this paper we examine the impacts of rural community activities that are pervasive in tropical regions on mixed‐species flocks of birds in a unique coastal tropical dry forest ecosystem, with the aim of advancing both our understanding of mixed‐species associations and how best to conserve them. We examined the effects of small‐scale clearing of trees and livestock grazing on mixed flocks in two vegetation types in the highly threatened Tumbesian region of Ecuador. Because the fitness benefits of flocking come from a reduced risk of predation or enhanced feeding efficiencies, or both, habitat degradation could lead to changes in the benefits of flocking and thus flock characteristics. We predicted that, in more disturbed vegetation, flocks would have fewer species and individuals and that species would show lower flocking propensities and feeding efficiencies. Based on observations of 431 flocks, we found that these predictions were supported in tropical dry forest but not always in arid scrub vegetation. Less disturbed tropical dry forest had greater mean species richness per flock than more disturbed tropical dry forest, but mean species richness per flock did not differ between more and less disturbed arid scrub. Flock species richness and composition differed across the disturbance levels in tropical dry forest, but not in arid scrub. Many species had their highest flocking propensities and greatest foraging efficiencies in less disturbed, compared to more disturbed, vegetation. We show that existing park management, which allows community development and livestock grazing within national park borders, leads to degradation of the vegetation and disrupts species' interactions in tropical dry forest. We provide specific conservation recommendations to mitigate these disruptive influences. Examining intraspecific associations across diverse communities is of the utmost importance to both answering basic theoretical questions in community ecology and conserving species diversity in the face of anthropogenic landscape change.

Global environmental problems such as climate change are not bounded by national borders or scientific disciplines, and therefore require international, interdisciplinary teamwork to develop understandings of their causes and solutions. Interdisciplinary scientific work is difficult enough, but these challenges are often magnified when teams also work across national boundaries. The literature on the challenges of interdisciplinary research is extensive. However, research on international, interdisciplinary teams is nearly non-existent. Our objective is to fill this gap by reporting on results from a study of a large interdisciplinary, international National Science Foundation Partnerships for International Research and Education (NSF-PIRE) research project across the Americas. We administered a structured questionnaire to team members about challenges they faced while working together across disciplines and outside of their home countries in Argentina, Brazil, and Mexico. Analysis of the responses indicated five major types of barriers to conducting interdisciplinary, international research: integration, language, fieldwork logistics, personnel and relationships, and time commitment. We discuss the causes and recommended solutions to the most common barriers. Our findings can help other interdisciplinary, international research teams anticipate challenges, and develop effective solutions to minimize the negative impacts of these barriers to their research.

Oil palm (Elaeis guineensis) plantations are one of the most rapidly expanding agroecosystems in the tropics, including Latin America. While many studies have demonstrated that large oil palm monocultures (>100 ha) are detrimental to biodiversity, including mammals, little is known about the impact of small-scale oil palm plantations, especially in the Neotropics. Here we used a camera trapping survey to compare species richness, community structure, and relative abundances of mid to large-bodied terrestrial mammals in small-scale oil palm plantations (<100 ha) and secondary forest fragments within a highly modified landscape mosaic in the southeastern lowlands of Tabasco, Mexico. Contrary to our expectations, we found no differences in the overall mammal communities between the oil palm and forest fragments, including species richness or mean relative abundance. Individual species showed some apparent differences in their total detections between the two habitats, with 11 having greater detections in forest than oil palm, and only two with greater detections in oil palm. Further, oil palm sites were more similar to one another in terms of mammal community structure than the secondary forest fragments. We found that shorter distance to forest patches was related to higher mammal species richness in both forest fragments and oil palm plantations. Twelve terrestrial mammal species known to occur in forested areas in the state of Tabasco were never detected in either vegetation type in our surveys, highlighting the fact that the mammal community in this landscape had already been reduced to those species most resilient to human disturbance. Our findings suggest that small-scale oil palm plantations in this region are used at least to some degree by most mammals that are also found in the remaining secondary forest fragments in this landscape, but that access to nearby forest is important for these species. In order to recover more of the original mammal community of the region and prevent further reductions in biodiversity, conservation priorities should center around reducing hunting pressure, allowing forest regeneration and increasing connectivity between protected areas and along waterways.

General ecological methods and models that require a minimum amount of information yet are still able to inform conservation planning are particularly valuable. Nested subset analysis has been advocated as such a tool for the prediction of extinction-prone species and populations. However, such advocacy has not been without skepticism and debate, and in the majority of published examples assessing extinction vulnerability, actual extinctions are based on assumptions rather than direct evidence. Here, we empirically test the power of nested subset analysis to predict extinction-prone species, using documented Holocene insular mammal extinctions on three island archipelagos off the west coast of North America. We go on to test whether the introduction of invasive mammals promotes nestedness on islands via extinction. While all three archipelagos were significantly nested before and after the extinction events, nested subset analysis largely failed to predict extinction patterns. We also failed to detect any correlations between the degree of nestedness at the genus-level with area, isolation, or species richness and extinction risk. Biogeography tools, such as nested subset analysis, must be critically evaluated before they are prescribed widely for conservation planning. For these island archipelagos, it appears detailed natural history and taxa-specific ecology may prove critical in predicting patterns of extinction risk.