High Foraging Fidelity and Plant-Pollinator Network Dominance of Non-native Honeybees (Apis mellifera) in the Ecuadorian Andes.

Pollinator foraging fidelity (i.e., consistent and repeated visitation to a particular plant species or area) is poorly understood for most bee species, but is important information for both the conservation of plant and pollinator species and the ecosystem services they provide to humans. We used plant-pollinator surveys and mark-recapture of floral-visiting Hymenoptera to study the foraging fidelity and species interaction network properties of a plant-pollinator community in the tropical Andes of southern Ecuador. After marking 92 bees visiting six plant taxa along four 100-m transects between July 16th and July 31st of 2019, only honeybees were resighted at a recapture rate of 47.7% (41/86). During our surveys, we observed nine bee and two wasp taxa feeding from the flowers of 10 morphospecies of plants, and we found significantly low network nestedness and significantly high network-level specialization. Specialization (d') was also significant for honeybees and bumblebees and for three plant taxa. Overall, our findings indicated that feral, non-native honeybees in this region dominated the local plant-pollinator network, yet this species is acting as a specialist forager at the individual level. Our results suggest that honeybees may be replacing the pollination services of some native bees and wasps in the region, but more research is needed to determine the effectiveness of honeybee pollination for the local plants.

Orchid bees (Apidae, Euglossini) from Oil Palm Plantations in Eastern Amazon Have Larger but Not Asymmetrical Wings.

Phenotypic variation in both morphology and symmetry of individuals may appear due to environmental stress caused by land-use changes. Here, we evaluated fluctuating asymmetry (FA) and wing size variations of two orchid bee species, Euglossa ignita Smith, 1874 and Eulaema meriana (Olivier, 1789), comparing 11 wing traits. We sampled the individuals from legal reserves (LR), areas of permanent protection (APP), and oil palm plantations (PALM) in Eastern Amazonia. We calculated FA as the absolute difference between the wing measurements made in the right and left wings of specimens and both species' wing size. We corrected each FA measure for possible directional asymmetry bias by subtracting the mean value of the mean FA signed difference to each FA measure. We compared FA and the size of each wing trait of each species between land-use types using one-way ANOVAs. We found no effect of FA between land-use types, but we observed individuals of both species from PALM areas having larger wings than those from LR areas. Our results demonstrate that there seems to be a pressure exerted by land-use change associated with palm oil cultivation favoring individuals with larger wings, although both species had shown substantial permeability of oil palm.

Vertical foraging shifts in Hawaiian forest birds in response to invasive rat removal.

Worldwide, native species increasingly contend with the interacting stressors of habitat fragmentation and invasive species, yet their combined effects have rarely been examined. Direct negative effects of invasive omnivores are well documented, but the indirect effects of resource competition or those caused by predator avoidance are unknown. Here we isolated and examined the independent and interactive effects of invasive omnivorous Black rats (Rattus rattus) and forest fragment size on the interactions between avian predators and their arthropod prey. Our study examines whether invasive omnivores and ecosystem fragment size impact: 1) the vertical distribution of arthropod species composition and abundance, and 2) the vertical profile of foraging behaviors of five native and two non-native bird species found in our study system. We predicted that the reduced edge effects and greater structural complexity and canopy height of larger fragments would limit the total and proportional habitat space frequented by rats and thus limit their impact on both arthropod biomass and birds' foraging behavior. We experimentally removed invasive omnivorous Black rats across a 100-fold (0.1 to 12 ha) size gradient of forest fragments on Hawai'i Island, and paired foraging observations of forest passerines with arthropod sampling in the 16 rat-removed and 18 control fragments. Rat removal was associated with shifts in the vertical distribution of arthropod biomass, irrespective of fragment size. Bird foraging behavior mirrored this shift, and the impact of rat removal was greater for birds that primarily eat fruit and insects compared with those that consume nectar. Evidence from this model study system indicates that invasive rats indirectly alter the feeding behavior of native birds, and consequently impact multiple trophic levels. This study suggests that native species can modify their foraging behavior in response to invasive species removal and presumably arrival through behavioral plasticity.

Barriers and Solutions to Conducting Large International, Interdisciplinary Research Projects.

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.

Positive relationships between association strength and phenotypic similarity characterize the assembly of mixed-species bird flocks worldwide.

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 matrices 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.