Is Eriocnemis luciani meridae (Aves: Trochilidae) a diagnosable taxon and does it come from Venezuela, with remarks on the collectors Salomn Briceo and Walther Frederick Henninger

Eriocnemis luciani meridae was originally described from a single specimen collected in the late 19th century in western Venezuela. Subsequently a second specimen of E. luciani, also labelled Venezuela, has been taken as additional proof for a highly disjunct population of this hummingbird, which otherwise ranges from southwest Colombia to southern Peru (taxonomy-dependent). Eriocnemis l. meridae has been accepted by all of the global checklists of birds, but has been routinely ignored by Venezuelan sources. In an effort to resolve this dichotomy of treatment, we re-examined the specimens plumage in comparison with relevant material in two major European bird collections. We found that the characters used to erect E. l. meridae are only doubtfully or weakly expressed in the holotype and appear invisible in the Ohio specimen, but both are clearly referrable to the species E. luciani. Evidence that the second specimen was definitely collected in Venezuela is weak and its overall provenance is unclear. In contrast, an extensive historical investigation of the relevant collectors indicates that the holotype does appear to have been taken in Venezuela, although perhaps not in the precise locality indicated for it. This leaves an unusual situation whereby we consider the case for a separate Venezuelan endemic taxon to be unproven, but there is no incontrovertible reason to exclude the species from the countrys avifauna; according to recent niche modelling data it is best searched for in the Sierra Nevada of Mrida state. In contrast, a second subspecies of E. luciani, E. l. baptistae, described by the same authors as endemic to part of western Ecuador is, according to our reappraisal, clearly diagnosable and is upheld.

Diel niche partitioning of a plant-hummingbird network in the Atlantic forest of Brazil

Niche partitioning is an important mechanism that allows species to coexist. Within mutualistic interaction networks, diel niche partitioning, i.e., partitioning of resources throughout the day, has been neglected. We explored diel niche partitioning of a plant-hummingbird network in the Brazilian Atlantic forest for nine months. To evaluate diel patterns of hummingbird visits and nectar production, we used time-lapse cameras on focal flowers and repeated nectar volume and concentration measures, respectively. Additionally, we measured flower abundance around focal flowers and flower morphological traits. We did not observe diel partitioning for either hummingbirds or plants. Instead, hummingbirds appeared to specialize in different plant species, consistent with trophic niche partitioning, potentially resulting from competition. In contrast, plant species that co-flowered and shared hummingbird visits produced nectar during similar times, consistent with facilitation. Our focus on the fine-scale temporal pattern revealed that plants and hummingbirds appear to have different strategies for promoting co-existence.

Hummingbird community structure and nectar resources modulate the response of interspecific competition to forest conversion

On-going land-use change has profound impacts on biodiversity by filtering species that cannot survive in disturbed landscapes and potentially altering biotic interactions. In particular, how land-use change reshapes biotic interactions remains an open question. Here, we used selectivity experiments with nectar feeders in natural and converted forests to test the direct and indirect effects of land-use change on resource competition in Andean hummingbirds along an elevational gradient. Selectivity was defined as the time hummingbirds spent at high resource feeders when feeders with both low and high resource values were offered in the presence of other hummingbird species. Selectivity approximates the outcome of interspecific competition (i.e., the resource intake across competing species); in the absence of competition, birds should exhibit higher selectivity. We evaluated the indirect effect of forest conversion on selectivity, as mediated by morphological dissimilarity and flower resource abundance, using structural equation models. We found that forest conversion influenced selectivity at low and mid-elevations, but the influence of morphological dissimilarity and resource availability on selectivity varied between these elevations. At mid-elevation, selectivity was more influenced by the presence of morphologically similar competitors than by resource abundance while at low-elevation resource abundance was a more important predictor of selectivity. Our results suggest that selectivity is influenced by forest conversion, but that the drivers of these changes vary across elevation, highlighting the importance of considering context-dependent variation in the composition of resources and competitors when studying competition.

The interactive effects of environmental gradient and dispersal shape spatial phylogenetic patterns

Introduction

The emergence and maintenance of biodiversity include interacting environmental conditions, organismal adaptation to such conditions, and dispersal. To understand and quantify such ecological, evolutionary, and spatial processes, observation and interpretation of phylogenetic relatedness across space (e.g., phylogenetic beta diversity) is arguably a way forward as such patterns contain signals from all the processes listed above. However, it remains challenging to extract information about complex eco-evolutionary and spatial processes from phylogenetic patterns.

Methods

We link environmental gradients and organismal dispersal with phylogenetic beta diversity using a trait-based and eco-evolutionary model of diversification along environmental gradients. The combined effect of the environment and dispersal leads to distinct phylogenetic patterns between subsets of species and across geographical distances.

Results and discussion

Steep environmental gradients combined with low dispersal lead to asymmetric phylogenies, a high phylogenetic beta diversity, and the phylogenetic diversity between communities increases linearly along the environmental gradient. High dispersal combined with a less steep environmental gradient leads to symmetric phylogenies, low phylogenetic beta diversity, and the phylogenetic diversity between communities along the gradient increases in a sigmoidal form. By disentangling the eco-evolutionary mechanisms that link such interacting environment and dispersal effects and community phylogenetic patterns, our results improve understanding of biodiversity in general and help interpretation of observed phylogenetic beta diversity.

Variation in insulative feather structure in songbirds replacing each other along a tropical elevation gradient

High‐elevation organisms are expected to evolve physiological adaptations to cope with harsh environmental conditions. Yet, evidence for such adaptive differences, especially compared to closely related lowland taxa occurring along the same elevational gradient, is rare. Revisiting an anecdotal natural history observation by O. Bangs from 1899 and based on new measurements of museum specimens, we confirmed that the high‐elevation hermit wood wren (Henicorhina anachoreta) from the Sierra Nevada de Santa Marta, Colombia, has longer, more insulative feathers on the chest and back, than its lower‐elevation counterpart the grey‐breasted wood wren (H. leucophrys). However, we did not find evidence for the same specializations in subspecies of H. leucophrys that live at high elevations on other elevational gradients in the Colombian Andes, although similar adaptive solutions have arisen in separate mountain systems like the Himalayas. Adaptations in plumage may be associated with the recurrence of elevational species replacements throughout the tropics.

The evolution of the traplining pollinator role in hummingbirds: specialization is not an evolutionary dead end

Trapliners are pollinators that visit widely dispersed flowers along circuitous foraging routes. The evolution of traplining in hummingbirds is thought to entail morphological specialization through the reciprocal coevolution of longer bills with the long-tubed flowers of widely dispersed plant species. Specialization, such as that exhibited by traplining hummingbirds, is often viewed as both irreversible and an evolutionary dead end. We tested these predictions in a macroevolutionary framework. Specifically, we assessed the relationship between beak morphology and foraging and tested whether transitions to traplining are irreversible and lead to lower rates of diversification as predicted by the hypothesis that specialization is an evolutionary dead end. We find that there have been multiple independent transitions to traplining across the hummingbird phylogeny, but reversals have been rare or incomplete at best. Multiple independent lineages of trapliners have become morphologically specialized, convergently evolving relatively large bills for their body size. Traplining is not an evolutionary dead end however, since trapliners continue to give rise to new traplining species at a rate comparable to non-trapliners.

The evolution, ecology, and conservation of hummingbirds and their interactions with flowering plants

The ecological co-dependency between plants and hummingbirds is a classic example of a mutualistic interaction: hummingbirds rely on floral nectar to fuel their rapid metabolisms, and more than 7000 plant species rely on hummingbirds for pollination. However, threats to hummingbirds are mounting, with 10% of 366 species considered globally threatened and 60% in decline. Despite the important ecological implications of these population declines, no recent review has examined plant-hummingbird interactions in the wider context of their evolution, ecology, and conservation. To provide this overview, we (i) assess the extent to which plants and hummingbirds have coevolved over millions of years, (ii) examine the mechanisms underlying plant-hummingbird interaction frequencies and hummingbird specialization, (iii) explore the factors driving the decline of hummingbird populations, and (iv) map out directions for future research and conservation. We find that, despite close associations between plants and hummingbirds, acquiring evidence for coevolution (versus one-sided adaptation) is difficult because data on fitness outcomes for both partners are required. Thus, linking plant-hummingbird interactions to plant reproduction is not only a major avenue for future coevolutionary work, but also for studies of interaction networks, which rarely incorporate pollinator effectiveness. Nevertheless, over the past decade, a growing body of literature on plant-hummingbird networks suggests that hummingbirds form relationships with plants primarily based on overlapping phenologies and trait-matching between bill length and flower length. On the other hand, species-level specialization appears to depend primarily on local community context, such as hummingbird abundance and nectar availability. Finally, although hummingbirds are commonly viewed as resilient opportunists that thrive in brushy habitats, we find that range size and forest dependency are key predictors of hummingbird extinction risk. A critical direction for future research is to examine how potential stressors - such as habitat loss and fragmentation, climate change, and introduction of non-native plants - may interact to affect hummingbirds and the plants they pollinate.

Ecophylogenetics redux

Species' evolutionary histories shape their present-day ecologies, but the integration of phylogenetic approaches in ecology has had a contentious history. The field of ecophylogenetics promised to reveal the process of community assembly from simple indices of phylogenetic pairwise distances - communities shaped by environmental filtering were composed of closely related species, whereas communities shaped by competition were composed of less closely related species. However, the mapping of ecology onto phylogeny proved to be not so straightforward, and the field remains mired in controversy. Nonetheless, ecophylogenetic methods provided important advances across ecology. For example the phylogenetic distances between species is a strong predictor of pest and pathogen sharing, and can thus inform models of species invasion, coexistence and the disease dilution/amplification effect of biodiversity. The phylogenetic structure of communities may also provide information on niche space occupancy, helping interpret patterns of facilitation, succession and ecosystem functioning - with relevance for conservation and restoration - and the dynamics among species within foodwebs and metacommunities. I suggest leveraging advances in our understanding of the process of evolution on phylogenetic trees would allow the field to progress further, while maintaining the essence of the original vision that proved so seductive.

Global functional and phylogenetic structure of avian assemblages across elevation and latitude

Mountain systems are exceptionally species rich, yet the associated elevational gradients in functional and phylogenetic diversity and their consistency across latitude remain little understood. Here, we document how avian functional and phylogenetic diversity and structure vary along all major elevational gradients worldwide and uncover strong latitudinal differences. Assemblages in warm tropical lowlands and cold temperate highlands are marked by high functional overdispersion and distinctiveness, whereas tropical highlands and temperate lowlands appear strongly functionally clustered and redundant. We additionally find strong geographic variation in the interplay of phylogenetic and functional structure, with strongest deviations between the two in temperate highlands. This latitudinal and elevational variation in assemblage functional structure is underpinned by nuanced shifts in the position, shape and composition of multivariate trait space. We find that, independent of latitude, high-elevation assemblages emerge as exceptionally susceptible to functional change.

Assembly rules in a resource gradient: Competition and abiotic filtering determine the structuring of plant communities in stressful environments

The relative importance of different community assembly mechanisms varies depending on the environment. According to the stress-dominance hypothesis (SDH), assembly mechanisms range from strong abiotic filtering to competition as the environment becomes more favourable. Most evidence for the SDH comes from studies in gradients of conditions (i.e. abiotic environmental factors that influence the functioning of organisms but are not consumed by them). However, we hypothesized that in resource gradients, competition increases as abiotic filtering becomes stronger. To test our hypothesis, we set up eight plots at different sites along an abiotic severity gradient in the Brazilian semi-arid region (BSAR). In each plot, we identified and measured each woody plant species found, and we recorded 11 functional traits of the main species, dividing the traits into alpha (competition effects) and beta (abiotic filtering effects). We investigated the presence of phylogenetic signal in the traits, the community phylogenetic and phenotypic patterns, and associated the variation in these patterns with the availability of water and soil nutrients. We found phylogenetic signal for most (91%) of the traits analysed. The phylogenetic patterns varied from clustered in stressful sites to random or overdispersed in favourable sites, and we concluded that these phylogenetic patterns were the result of historical processes influencing community assembly in different environments in the BSAR. In general, the phenotypic patterns varied from clustered at the most stressful end to random at less stressful sites. Our results show that in resource gradients, any restriction of the resource (hydric or edaphic) intensifies abiotic filtering and, at the same time, increases the competitive hierarchy among species. On the other hand, stochastic processes seem to have a stronger influence under more favourable abiotic conditions, where abiotic filtering and competition are weaker. Thus, we conclude that the SDH is not supported in resource gradients.

Identifying models of trait-mediated community assembly using random forests and approximate Bayesian computation

Ecologists often use dispersion metrics and statistical hypothesis testing to infer processes of community formation such as environmental filtering, competitive exclusion, and neutral species assembly. These metrics have limited power in inferring assembly models because they rely on often-violated assumptions. Here, we adapt a model of phenotypic similarity and repulsion to simulate the process of community assembly via environmental filtering and competitive exclusion, all while parameterizing the strength of the respective ecological processes. We then use random forests and approximate Bayesian computation to distinguish between these models given the simulated data. We find that our approach is more accurate than using dispersion metrics and accounts for uncertainty in model selection. We also demonstrate that the parameter determining the strength of the assembly processes can be accurately estimated. This approach is available in the R package CAMI; Community Assembly Model Inference. We demonstrate the effectiveness of CAMI using an example of plant communities living on lava flow islands.

Body mass as a supertrait linked to abundance and behavioral dominance in hummingbirds: A phylogenetic approach

Body mass has been considered one of the most critical organismal traits, and its role in many ecological processes has been widely studied. In hummingbirds, body mass has been linked to ecological features such as foraging performance, metabolic rates, and cost of flying, among others. We used an evolutionary approach to test whether body mass is a good predictor of two of the main ecological features of hummingbirds: their abundances and behavioral dominance. To determine whether a species was abundant and/or behaviorally dominant, we used information from the literature on 249 hummingbird species. For abundance, we classified a species as "plentiful" if it was described as the most abundant species in at least part of its geographic distribution, while we deemed a species to be "behaviorally dominant" when it was described as pugnacious (notably aggressive). We found that plentiful hummingbird species had intermediate body masses and were more phylogenetically related to each other than expected by chance. Conversely, behaviorally dominant species tended to have larger body masses and showed a random pattern of distribution in the phylogeny. Additionally, small-bodied hummingbird species were not considered plentiful by our definition and did not exhibit behavioral dominance. These results suggest a link between body mass, abundance, and behavioral dominance in hummingbirds. Our findings indicate the existence of a body mass range associated with the capacity of hummingbird species to be plentiful, behaviorally dominant, or to show both traits. The mechanisms behind these relationships are still unclear; however, our results provide support for the hypothesis that body mass is a supertrait that explains abundance and behavioral dominance in hummingbirds.

Integrating morphology and kinematics in the scaling of hummingbird hovering metabolic rate and efficiency

Wing kinematics and morphology are influential upon the aerodynamics of flight. However, there is a lack of studies linking these variables to metabolic costs, particularly in the context of morphological adaptation to body size. Furthermore, the conversion efficiency from chemical energy into movement by the muscles (mechanochemical efficiency) scales with mass in terrestrial quadrupeds, but this scaling relationship has not been demonstrated within flying vertebrates. Positive scaling of efficiency with body size may reduce the metabolic costs of flight for relatively larger species. Here, we assembled a dataset of morphological, kinematic, and metabolic data on hovering hummingbirds to explore the influence of wing morphology, efficiency, and mass on hovering metabolic rate (HMR). We hypothesize that HMR would decline with increasing wing size, after accounting for mass. Furthermore, we hypothesize that efficiency will increase with mass, similarly to other forms of locomotion. We do not find a relationship between relative wing size and HMR, and instead find that the cost of each wingbeat increases hyperallometrically while wingbeat frequency declines with increasing mass. This suggests that increasing wing size is metabolically favourable over cycle frequency with increasing mass. Further benefits are offered to larger hummingbirds owing to the positive scaling of efficiency.

Drivers of Phylogenetic Assemblage Structure of the Furnariides, a Widespread Clade of Lowland Neotropical Birds

Species co-occurrence in local assemblages is shaped by distinct processes at different spatial and temporal scales. Here we focus on historical explanations and examine the phylogenetic structure of local assemblages of the Furnariides clade (Aves: Passeriformes), assessing the influence of diversification rates on the assembly and species co-occurrence within those assemblages. Using 120 local assemblages across Bolivia and Argentina and a nearly complete phylogeny for the clade, we analyzed assemblage phylogenetic structure, applying a recently developed model (DAMOCLES, or dynamic assembly model of colonization, local extinction, and speciation) accounting for the historical processes of speciation, colonization, and local extinction. We also evaluated how diversification rates determine species co-occurrence. We found that the assembly of Furnariides assemblages can be explained largely by speciation, colonization, and local extinction without invoking current local species interactions. Phylogenetic structure of open habitat assemblages mainly showed clustering, characterized by faster rates of colonization and local extinction than in forest habitats, whereas forest habitat assemblages were congruent with the model's equal rates expectation, thus highlighting the influence of habitat preferences on assembly and co-occurrence patterns. Our results suggest that historical processes are sufficient to explain local assemblage phylogenetic structure, while there is little evidence for species ecological interactions in avian assemblage diversity and composition.

Divergent trends in functional and phylogenetic structure in reptile communities across Africa

Despite extensive research on ecological community compositions, general patterns across large-scale environmental gradients have remained unclear. A widely used explanatory model is the stress dominance hypothesis (SDH), predicting that the relative influence of environmental filtering is greater in stressful habitats while competition is more important in benign environments. Here, we test the SDH using African squamates as a model system to facilitate general predictions on community structures amidst changing global environments. For the first time we investigate changes in functional, phylogenetic and species diversity across continental, environmental gradients within a multidimensional, phylogenetically informed approach. Results suggest that phylogenetic patterns of African squamates were likely shaped by clade-specific biogeographic histories, whereas functional structure reflects SDH predictions. We further detected significant structuring at both local and regional spatial scales, emphasizing the impact of regional-historical processes on local assemblages, and the need for broad conceptual frameworks to detect general patterns of community composition.

The biogeographic drivers of reptile diversity are poorly understood relative to other animal groups. Here, using a dataset of distributions of African squamates, the authors show that environmental filtering explains diversity in stressful habitats while competition explains diversity in benign habitats.

Land use change has stronger effects on functional diversity than taxonomic diversity in tropical Andean hummingbirds

Land use change modifies the environment at multiple spatial scales, and is a main driver of species declines and deterioration of ecosystem services. However, most of the research on the effects of land use change has focused on taxonomic diversity, while functional diversity, an important predictor of ecosystem services, is often neglected. We explored how local and landscape scale characteristics influence functional and taxonomic diversity of hummingbirds in the Andes Mountains in southern Ecuador. Data was collected in six landscapes along a land use gradient, from an almost intact landscape to one dominated by cattle pastures. We used point counts to sample hummingbirds from 2011 to 2012 to assessed how local factors (i.e., vegetation structure, flowering plants richness, nectar availability) and landscape factors (i.e., landscape heterogeneity, native vegetation cover) influenced taxonomic and functional diversity. Then, we analyzed environment – trait relationships (RLQ test) to explore how different hummingbird functional traits influenced species responses to these factors. Taxonomic and functional diversity of hummingbirds were positively associated with landscape heterogeneity but only functional diversity was positively related to native vegetation coverage. We found a weak response of taxonomic and functional diversity to land use change at the local scale. Environment‐trait associations showed that body mass of hummingbirds likely influenced species sensitivity to land use change. In conclusion, landscape heterogeneity created by land use change can positively influence hummingbird taxonomic and functional diversity; however, a reduction of native vegetation cover could decrease functional diversity. Given that functional diversity can mediate ecosystem services, the conservation of native vegetation cover could play a key role in the maintenance of hummingbird pollination services in the tropical Andes. Moreover, there are particular functional traits, such as body mass, that increase a species sensitivity to land use change.

Strong influence of palaeoclimate on the structure of modern African mammal communities

Ecological research often assumes that species are adapted to their current climatic environments. However, climate fluctuations over geologic timescales have influenced species dispersal and extinction, which in turn may affect community structure. Modern community structure is likely to be the product of both palaeoclimate and modern climate, with the relative degrees of influence of past and present climates unknown. Here, we assessed the influence of climate at different time periods on the phylogenetic and functional trait structure of 203 African mammal communities. We found that the climate of the mid-Holocene (approx. 6000 years ago) and Last Glacial Maximum (approx. 22 000 years ago) were frequently better predictors of community structure than modern climate for mammals overall, carnivorans and ungulates. Primate communities were more strongly influenced by modern climate than palaeoclimate. Overall, community structure of African mammals appears to be related to the ecological flexibility of the groups considered here and the regions of continental Africa that they occupy. Our results indicate that the future redistribution, expansion and contraction of particular biomes due to human activity, such as climate and land-use change, will differentially affect mammal groups that vary in their sensitivity to environmental change.

The role of environment, dispersal and competition in explaining reduced co-occurrence among related species

The composition of ecological assemblages depends on a variety of factors including environmental filtering, biotic interactions and dispersal limitation. By evaluating the phylogenetic pattern of assemblages, we gain insight into the relative contribution of these mechanisms to generating observed assemblages. We address some limitations in the field of community phylogenetics by using simulations, biologically relevant null models, and cost distance analysis to evaluate simultaneous mechanisms leading to observed patterns of co-occurrence. Building from past studies of phylogenetic community structure, we applied our approach to hummingbird assemblages in the Northern Andes. We compared the relationship between relatedness and co-occurrence among predicted assemblages, based on estimates of suitable habitat and dispersal limitation, and observed assemblages. Hummingbird co-occurrence peaked at intermediate relatedness and decreased when a closely-related species was present. This result was most similar to simulations that included simultaneous effects of phylogenetic conservatism and repulsion. In addition, we found older sister taxa were only weakly more separated by geographic barriers, suggesting that time since dispersal is unlikely to be the sole factor influencing co-occurrence of closely related species. Our analysis highlights the role of multiple mechanisms acting simultaneously, and provides a hypothesis for the potential importance of competition at regional scales.

Persistent bill and corolla matching despite shifting temporal resources in tropical hummingbird-plant interactions

By specialising on specific resources, species evolve advantageous morphologies to increase the efficiency of nutrient acquisition. However, many specialists face variation in resource availability and composition. Whether specialists respond to these changes depends on the composition of the resource pulses, the cost of foraging on poorly matched resources, and the strength of interspecific competition. We studied hummingbird bill and plant corolla matching during seasonal variation in flower availability and morphology. Using a hierarchical Bayesian model, we accounted for the detectability and spatial overlap of hummingbird-plant interactions. We found that despite seasonal pulses of flowers with short-corollas, hummingbirds consistently foraged on well-matched flowers, leading to low niche overlap. This behaviour suggests that the costs of searching for rare and more specialised resources are lower than the benefit of switching to super-abundant resources. Our results highlight the trade-off between foraging efficiency and interspecific competition, and underline niche partitioning in maintaining tropical diversity.

Process-Based Species Pools Reveal the Hidden Signature of Biotic Interactions Amid the Influence of Temperature Filtering

A persistent challenge in ecology is to tease apart the influence of multiple processes acting simultaneously and interacting in complex ways to shape the structure of species assemblages. We implement a heuristic approach that relies on explicitly defining species pools and permits assessment of the relative influence of the main processes thought to shape assemblage structure: environmental filtering, dispersal limitations, and biotic interactions. We illustrate our approach using data on the assemblage composition and geographic distribution of hummingbirds, a comprehensive phylogeny and morphological traits. The implementation of several process-based species pool definitions in null models suggests that temperature-but not precipitation or dispersal limitation-acts as the main regional filter of assemblage structure. Incorporating this environmental filter directly into the definition of assemblage-specific species pools revealed an otherwise hidden pattern of phylogenetic evenness, indicating that biotic interactions might further influence hummingbird assemblage structure. Such hidden patterns of assemblage structure call for a reexamination of a multitude of phylogenetic- and trait-based studies that did not explicitly consider potentially important processes in their definition of the species pool. Our heuristic approach provides a transparent way to explore patterns and refine interpretations of the underlying causes of assemblage structure.

The effect of spatial scale on relative influences of assembly processes in temperate stream fish assemblages

Understanding how biotic and abiotic processes influence community assembly is a fundamental aim in ecology. Although spatial scales at which communities are studied may affect the relative importance of such assembly processes, spatial influences on community assembly have not been thoroughly addressed. We tested how spatial scale affects inferences of habitat filtering and competitive exclusion assembly processes in darter (Percidae: Etheostomatinae) assemblages across four temperate stream systems. We predicted competitive exclusion would influence assembly in fine-scale assemblages, and habitat filtering would be more influential as spatial scale increased. Moreover, we assumed that habitat heterogeneity would increase with scale, and consequently alleviate direct competitive exclusion acting at finer scales. Using a framework that incorporated genetic relatedness, morphological traits, and habitat use among co-occurring darter species, we identified ecological and evolutionary patterns of structure, which allowed us to elucidate processes of assembly. Based on phylogenetic structure, assemblages showed an increase in habitat filtering (i.e., increased phylogenetic clustering) as we scaled up from fine to intermediate assemblages; however, we found mixed signals for habitat filtering and competitive exclusion at the broadest spatial scale. While habitat filtering was found to have an overall high relative importance during assembly, we also found influence of competitive exclusion processes based on limited morphological similarity among co-occurring species. Our results generally support an increased influence of habitat filtering processes in broader scale assemblages. Moreover, we suggest that habitat filtering and competitive exclusion processes act simultaneously during assembly, although the relative influence of each process may be spatial-scale dependent.

Climate and species richness predict the phylogenetic structure of African mammal communities

We have little knowledge of how climatic variation (and by proxy, habitat variation) influences the phylogenetic structure of tropical communities. Here, we quantified the phylogenetic structure of mammal communities in Africa to investigate how community structure varies with respect to climate and species richness variation across the continent. In addition, we investigated how phylogenetic patterns vary across carnivores, primates, and ungulates. We predicted that climate would differentially affect the structure of communities from different clades due to between-clade biological variation. We examined 203 communities using two metrics, the net relatedness (NRI) and nearest taxon (NTI) indices. We used simultaneous autoregressive models to predict community phylogenetic structure from climate variables and species richness. We found that most individual communities exhibited a phylogenetic structure consistent with a null model, but both climate and species richness significantly predicted variation in community phylogenetic metrics. Using NTI, species rich communities were composed of more distantly related taxa for all mammal communities, as well as for communities of carnivorans or ungulates. Temperature seasonality predicted the phylogenetic structure of mammal, carnivoran, and ungulate communities, and annual rainfall predicted primate community structure. Additional climate variables related to temperature and rainfall also predicted the phylogenetic structure of ungulate communities. We suggest that both past interspecific competition and habitat filtering have shaped variation in tropical mammal communities. The significant effect of climatic factors on community structure has important implications for the diversity of mammal communities given current models of future climate change.

A new dynamic null model for phylogenetic community structure

Phylogenies are increasingly applied to identify the mechanisms structuring ecological communities but progress has been hindered by a reliance on statistical null models that ignore the historical process of community assembly. Here, we address this, and develop a dynamic null model of assembly by allopatric speciation, colonisation and local extinction. Incorporating these processes fundamentally alters the structure of communities expected due to chance, with speciation leading to phylogenetic overdispersion compared to a classical statistical null model assuming equal probabilities of community membership. Applying this method to bird and primate communities in South America we show that patterns of phylogenetic overdispersion – often attributed to negative biotic interactions – are instead consistent with a species neutral model of allopatric speciation, colonisation and local extinction. Our findings provide a new null expectation for phylogenetic community patterns and highlight the importance of explicitly accounting for the dynamic history of assembly when testing the mechanisms governing community structure.

Taxonomic, phylogenetic, and trait Beta diversity in South American hummingbirds

Comparison of the taxonomic, phylogenetic, and trait dimensions of beta diversity may uncover the mechanisms that generate and maintain biodiversity, such as geographic isolation, environmental filtering, and convergent adaptation. We developed an approach to predict the relationship between environmental and geographic distance and the dimensions of beta diversity. We tested these predictions using hummingbird assemblages in the northern Andes. We expected taxonomic beta diversity to result from recent geographic barriers limiting dispersal, and we found that cost distance, which includes barriers, was a better predictor than Euclidean distance. We expected phylogenetic beta diversity to result from historical connectivity and found that differences in elevation were the best predictors of phylogenetic beta diversity. We expected high trait beta diversity to result from local adaptation to differing environments and found that differences in elevation were correlated with trait beta diversity. When combining beta diversity dimensions, we observe that high beta diversity in all dimensions results from adaption to different environments between isolated assemblages. Comparisons with high taxonomic, low phylogenetic, and low trait beta diversity occurred among lowland assemblages separated by the Andes, suggesting that geographic barriers have recently isolated lineages in similar environments. We provide insight into mechanisms governing hummingbird biodiversity patterns and provide a framework that is broadly applicable to other taxonomic groups.

Asynchrony of taxonomic, functional and phylogenetic diversity in birds

AIM

We assessed the temporal trends of taxonomic, functional and phylogenetic diversities in the French avifauna over the last two decades. Additionally, we investigated whether and how this multifaceted approach to biodiversity dynamics can reveal an increasing similarity of local assemblages in terms of species, traits and/or lineages.

LOCATION

France.

METHODS

We analysed a large-scale dataset that recorded annual changes in the abundance of 116 breeding birds in France between 1989 and 2012. We decomposed and analysed the spatio-temporal dynamics of taxonomic, phylogenetic and functional diversities and each of their α-, β- and γ-components. We also calculated the trend in the mean specialization of bird communities to track the relative success of specialist versus generalist species within communities during the same period.

RESULTS

We found large variation within and among the temporal trends of each biodiversity facet. On average, we found a marked increase in species and phylogenetic diversity over the period considered, but no particular trend was found for functional diversity. Conversely, changes in β-diversities for the three facets were characterized by independent and nonlinear trends. We also found a general increase in the local occurrence and abundance of generalist species within local communities.

MAIN CONCLUSIONS

These results highlight a relative asynchrony of the different biodiversity facets occurring at large spatial scales. We show why a multifaceted approach to biodiversity dynamics is needed to better describe and understand changes in community composition in macroecology and conservation biogeography.

Expanding the understanding of local community assembly in adaptive radiations

Communities are thought to be assembled by two types of filters: by the environment relating to the fundamental niche and by biotic interactions relating to the realized niche. Both filters include parameters related to functional traits and their variation along environmental gradients. Here, we infer the general importance of environmental filtering of a functional trait determining local community assembly within insular adaptive radiations on the example of Caribbean Anolis lizards. We constructed maps for the probability of presence of Anolis ecomorphs (ecology-morphology-behavior specialists) on the Greater Antilles and overlaid these to estimate ecomorph community completeness (ECC) over the landscape. We then tested for differences in environmental parameter spaces among islands for real and cross-fitted ECC values to see whether the underlying assembly filters are deterministic (i.e., similar among islands). We then compared information-theoretic models of climatic and landscape parameters among Greater Antillean islands and inferred whether body mass as functional trait determines ECC. We found areas with high ECC to be strongly correlated with environmental filters, partly related to elevation. The environmental parameters influencing high ECC differed among islands. With the exception of the Jamaican twig ecomorph (which we suspect to be misclassified), smaller ecomorphs were more restricted to higher elevations than larger ones which might reflect filtering on the basis of differential physiological restrictions of ecomorphs. Our results in Anolis show that local community assembly within adaptive island radiations of animals can be determined by environmental filtering of functional traits, independently from species composition and realized environmental niche space.

How competitive trade-offs limit elevation ranges for temperate-breeding hummingbirds

One intriguing hypothesis about range limits of species along environmental gradients is that interspecific interference competition limits the activity of the better exploitation competitor. The hypothesis works if the costs of interference and (or) exploitation vary along the gradient. However, in some systems, species turnover happens over gradients that may be too short to induce changes in costs associated with competition. An example is breeding Black-chinned Hummingbirds (Archilochus alexandri (Bourcier and Mulsant, 1846)) and Broad-tailed Hummingbirds (Selasphorus platycercus (Swainson, 1827)) in western Colorado, USA, where turnover happens over ∼400 m. We recorded foraging and chasing activity of the two species at feeders and found that their foraging activity changed with elevation but interspecific competition did not. Because the foraging activity of the two species changed inversely with each other, it may be the presence of Black-chinned Hummingbirds rather than active interference that limits the activity of Broad-tailed Hummingbirds. Importantly, the relationship between foraging activity and elevation depended on the distance between the two feeders, which shows that relationships with elevation are contingent on other factors such as spatial distribution of resources. Our results suggest that interspecific differences in flight performance are not manifested over the short elevation gradient and do not account for changes in activity. Flight performance may indirectly affect patterns in breeding-season activity by influencing how species interact with other competitors during the nonbreeding season.

Filtering across spatial scales: phylogeny, biogeography and community structure in bumble bees

Despite the expansion of phylogenetic community analysis to understand community assembly, few studies have used these methods on mobile organisms and it has been suggested the local scales that are typically considered may be too small to represent the community as perceived by organisms with high mobility. Mobility is believed to allow species to mediate competitive interactions quickly and thus highly mobile species may appear randomly assembled in local communities. At larger scales, however, biogeographical processes could cause communities to be either phylogenetically clustered or even. Using phylogenetic community analysis we examined patterns of relatedness and trait similarity in communities of bumble bees (Bombus) across spatial scales comparing: local communities to regional pools, regional communities to continental pools and the continental community to a global species pool. Species composition and data on tongue lengths, a key foraging trait, were used to test patterns of relatedness and trait similarity across scales. Although expected to exhibit limiting similarity, local communities were clustered both phenotypically and phylogenetically. Larger spatial scales were also found to have more phylogenetic clustering but less trait clustering. While patterns of relatedness in mobile species have previously been suggested to exhibit less structure in local communities and to be less clustered than immobile species, we suggest that mobility may actually allow communities to have more similar species that can simply limit direct competition through mobility.