β-diversity scaling patterns are consistent across metrics and taxa

We thank the University of St Andrews Bioinformatics Unit (Wellcome Trust ISSF grant 105621/Z/14/Z). L.H.A.was supported by Fundação para a Ciência e Tecnologia, Portugal (POPH/FSE SFRH/BD/90469/2012), A.E.M. by the ERC BioTIME (250189) and BioCHANGE (727440), and B.J.M. by USDA Hatch grant to MAFES #1011538 and NSF ABI grant #1660000. The BioTIME database was funded by ERC AdG BioTIME (250189) and ERC PoC BioCHANGE (727440).β‐diversity (variation in community composition) is a fundamental component of biodiversity, with implications for macroecology, community ecology and conservation. However, its scaling properties are poorly understood. Here, we systematically assessed the spatial scaling of β‐diversity using 12 empirical large‐scale datasets including different taxonomic groups, by examining two conceptual types of β‐diversity and explicitly considering the turnover and nestedness components. We found highly consistent patterns across datasets. Multiple‐site β‐diversity (i.e. variation across multiple sites) scaling curves were remarkably consistent, with β‐diversity decreasing with sampled area according to a power law. For pairwise dissimilarities, the rates of increase of dissimilarity with geographic distance remained largely constant across scales, while grain size (or scale level) had a stronger effect on overall dissimilarity. In both analyses, turnover was the main contributor to β‐diversity, following total β‐diversity patterns closely, while the nestedness component was largely insensitive to scale changes. Our results highlight the importance of integrating both inter‐ and intraspecific aggregation patterns across spatial scales, which underpin substantial differences in community structure from local to regional scales.PostprintPeer reviewe

Long‐Distance Natal Dispersal Is Relatively Frequent and Correlated with Environmental Factors in a Widespread Raptor

Dispersal is a critical process influencing population dynamics and responses to global change. Long‐distance dispersal (LDD) can be especially important for gene flow and adaptability, although little is known about the factors influencing LDD because studying large‐scale movements is challenging and LDD tends to be observed less frequently than shorter‐distance dispersal (SDD). We sought to understand patterns of natal dispersal at a large scale, specifically aiming to understand the relative frequency of LDD compared to SDD and correlates of dispersal distances. We used bird banding and encounter data for American kestrels (Falco sparverius) to investigate the effects of sex, migration strategy, population density, weather, year and agricultural land cover on LDD frequency, LDD distance and SDD distance in North America from 1961 to 2015. Nearly half of all natal dispersal (48.9%) was LDD (classified as \u3e30 km), and the likelihood of LDD was positively associated with the proportion of agricultural land cover around natal sites. Correlates of distance differed between LDD and SDD movements. LDD distance was positively correlated with latitude, a proxy for migration strategy, suggesting that migratory individuals disperse farther than residents. Distance of LDD in males was positively associated with maximum summer temperature. We did not find sex‐bias or an effect of population density in LDD distance or frequency. Within SDD, females tended to disperse farther than males, and distance was positively correlated with density. Sampling affected all responses, likely because local studies more frequently capture SDD within study areas. Our findings that LDD occurs at a relatively high frequency and is related to different proximate factors from SDD, including a lack of sex‐bias in LDD, suggest that LDD may be more common than previously reported, and LDD and SDD may be distinct processes rather than two outcomes originating from a single dispersal distribution. To our knowledge, this is the first evidence that LDD and SDD may be separate processes in an avian species, and suggests that environmental change may have different outcomes on the two processes

Human‐associated species dominate passerine communities across the United States

Aim: Human development and agriculture can have transformative and homogenizing effects on natural systems, shifting the composition of ecological communities towards non-native and native species that tolerate or thrive under human-dominated conditions. These impacts cannot be fully captured by summarizing species presence, as they include dramatic changes to patterns of species abundance. However, how human land use patterns and species invasions intersect to shape patterns of abundance and dominance within ecological communities is poorly understood even in well-known taxa. Location: Conterminous United States. Time period: 2010–2012. Major taxa studied: Passeriformes. Methods: We analyse continental-scale monitoring data to study the proportional abundance of non-native and native synanthropic species within passerine bird communities. Synanthropic species are those that benefit from an association with humans. We estimate how the amount and configuration of human development and agriculture relate to the degree to which human-associated species dominate passerine communities across the continent. Results: Human-associated species comprised the majority of detected passerine individuals across two-thirds of bird surveys. Non-native and synanthropic species responded differently to land cover and reached highest relative abundance in different portions of the continent. The proportional abundance of synanthropic birds increased rapidly with development, but was not related to the configuration of land cover. The proportion of non-native individuals was higher when intensively-used land cover was more aggregated. Main conclusions: Even low amounts of intensively-used lands were associated with a dramatic reshaping of passerine communities, with consequences for patterns of relative abundance across the continent

Data Set for Patterns and Mechanisms of Heterogeneous Breeding Distribution Shifts of North American Migratory Birds

There is widespread evidence that species distributions are shifting in response to climate change. Warming temperatures and climate niche constraints are hypothesized drivers of northward shifts in temperate migratory bird breeding distributions, but heterogeneity in the direction of distribution shifts suggests that the climate niche hypothesis does not explain all changes in distributions. We propose that changes in the costs and benefits of migration are related to dampened seasonal differences between breeding and winter areas, sensitivity to supplemental cues, a mismatch-driven fitness gradient, or a combination of these drivers may explain southward distribution shifts. We examined latitudinal shifts in breeding distribution centroids for 73 species of migratory birds from 1994 - 2017 across eastern, central, and western regions of North America using Breeding Bird Survey data and tested if life history characteristics and population status explain shift patterns. We found that 44% of regional centroid shifts were southward, 55% were northward, and several species shifted in different directions in different regions. Migratory strategy and protandry predicted breeding distribution centroid shifts, although they tended to be more predictive of northward shifts than southward shifts. However, there was evidence that supplemental cues explained some southward shifts because herbivorous birds tended to shift southward compared to insectivores, or raptors that shifted northward. Shifts in centroids were not explained by trends in abundance, suggesting that centroid shifts were not attributable to population declines or increases at distribution margins. Our results show the prevalence of heterogeneous breeding distribution shifts, including often overlooked southward shifts, and suggest that more work is needed to develop alternative hypotheses that would explain southward shifts in distributions