Alex Pigot

University College London | UCL · Department of Genetics, Evolution and Environment (GEE)

Human activities are driving rapid defaunation of Earth's ecosystems through increasing rates of extinction. However, the ecological consequences of species loss remain unclear, in part due to the limited availability of high‐resolution functional trait data. To address this, we assess how predicted extinctions will reshape avian functional diversi...

Temperature overshoot pathways entail exceeding a specified global warming level (e.g. 1.5°C or 2°C) followed by a decline in warming, achieved through anthropogenically enhanced CO 2 removal from the atmosphere. However, risks to biodiversity from temperature overshoot pathways are poorly described. Here, we explore biodiversity risks from oversho...

Aim The coexistence and turnover of species along elevation gradients makes tropical mountains hotspots of biodiversity. However, understanding the historical processes through which species arising in geographic isolation (i.e. allopatry) assemble along the same mountain slope (i.e. sympatry) remains a major challenge. Multiple models have been pr...

Functional traits offer a rich quantitative framework for developing and testing theories in evolutionary biology, ecology and ecosystem science. However, the potential of functional traits to drive theoretical advances and refine models of global change can only be fully realised when species-level information is complete. Here we present the AVON...

Biological invasions pose one of the most severe environmental challenges of the twenty‐first century. A longstanding idea is that invasion risk is predictable based on the phylogenetic distance – and hence ecological resemblance – between non‐native and native species. However, current evidence is contradictory. To explain these mixed results, it...

The cover image is based on the Letter AVONET: morphological, ecological and geographical data for all birds by Tobias et al., https://doi.org/10.1111/ele.13898. The sword‐billed hummingbird (Ensifera ensifera) is exquisitely adapted to its trophic niche as an aerial pollinator of flowerings plants (angiosperms) in the high Andes. A new global data...

Land-use change is the leading driver of global biodiversity loss thus characterising its impacts on the functional structure of ecological communities is an urgent challenge. Using a database describing vertebrate assemblages in different land uses, we assess how the type and intensity of land use affect the functional diversity of vertebrates glo...

One of landscape ecology’s main goals is to unveil how biodiversity is impacted by habitat transformation. However, the discipline suffers from significant context dependency in observed spatial and temporal trends, hindering progress towards understanding the mechanisms driving species declines and preventing the development of accurate estimates...

Climate change causes shifts in species ranges globally. Terrestrial plant species often lag behind temperature shifts, and it is unclear to what extent animal‐dispersed plants can track climate change. Here, we estimate the ability of bird‐dispersed plant species to track future temperature change on a tropical mountain. Tropical elevational gradi...

Human impacts reshape ecological communities through the extinction and introduction of species. The combined impact of these factors depends on whether non-native species fill the functional roles of extinct species, thus buffering the loss of functional diversity. This question has been difficult to address, because comprehensive information abou...

Low-elevation regions harbour the majority of the world’s species diversity compared to high-elevation areas. This global gradient suggests that lowland species have had more time to diversify, or that net diversification rates have been higher in the lowlands. However, highlands seem to be cradles of diversity as they contain many young endemics,...

Priority effects can play a fundamental role in the assembly of ecological communities, but how they shape the dynamics of biodiversity over macroevolutionary timescales remains unclear. Here we develop and analyse a metacommunity model combining local priority effects with niche evolution, speciation and extinction. We show that by promoting the p...

The unabating rise in the number of species introduced outside of their native range makes predicting the spread of alien species an urgent challenge. Most predictions use models of the ecological niche of a species to identify suitable areas for invasion, but these predictions may have limited accuracy. Here, using the global alien avifauna, we de...

Despite biological invasions are one of the main environmental problems of the twenty-first century, there is still no theoretical or empirical agreement on whether a high phylogenetic relatedness between exotic and native species positively or negatively affect invasion success. To resolve this conundrum, it has been proposed that the effect might...

Classical ecological theory posits that species partition resources such that each species occupies a unique resource niche. In general, the availability of more resources allows more species to co‐occur. Thus, a strong relationship between communities of consumers and their resources is expected. However, correlations may be influenced by other la...

The origin, distribution, and function of biological diversity are fundamental themes of ecology and evolutionary biology. Research on birds has played a major role in the history and development of these ideas, yet progress was for many decades limited by a focus on patterns of current diversity, often restricted to particular clades or regions. D...

Low elevation regions harbor the majority of the world’s species diversity compared to high elevation areas. This global elevational diversity gradient, suggests that lowland species have had more time to diversify, or that net diversification rates have been higher in the lowlands (either due to higher ecological limits or intrinsically higher div...

Classical ecological theory posits that species partition resources such that each species occupies a unique resource niche. In general, the availability of more resources allows more species to co‐occur. Thus, a strong relationship between communities of consumers and their resources is expected. However, correlations may be influenced by other la...

Urbanisation is driving rapid declines in species richness and abundance worldwide, but the general implications for ecosystem function and services remain poorly understood. Here, we integrate global data on bird communities with comprehensive information on traits associated with ecological processes to show that assemblages in highly urbanised e...

As anthropogenic climate change continues the risks to biodiversity will increase over time, with future projections indicating that a potentially catastrophic loss of global biodiversity is on the horizon1–3. However, our understanding of when and how abruptly this climate-driven disruption of biodiversity will occur is limited because biodiversit...

Urbanization is a major driver of local biodiversity losses, but the traits that determine whether species are able to tolerate urban environments remain poorly understood. Theory suggests that a larger brain should provide higher tolerance to urbanization by enhancing behavioral flexibility to cope with novel challenges. However, assembling empiri...

Animals have diversified into a bewildering variety of morphological forms exploiting a complex configuration of trophic niches. Their morphological diversity is widely used as an index of ecosystem function, but the extent to which animal traits predict trophic niches and associated ecological processes is unclear. Here we use the measurements of...

Insights into animal behaviour play an increasingly central role in species-focused conservation practice. However, progress towards incorporating behaviour into regional or global conservation strategies has been more limited, not least because standardized datasets of behavioural traits are generally lacking at wider taxonomic or spatial scales....

A key question in invasion biology is why some regions have more alien species than others. Here, we provide a general framework to answer this. We model alien species richness as a function of the number of species introduced (colonization pressure) and the probability that each species establishes, which is a function of propagule pressure (the n...

Human-mediated translocation of species to areas beyond their natural distribution (which results in ‘alien’ populations¹) is a key signature of the Anthropocene², and is a primary global driver of biodiversity loss and environmental change³. Stemming the tide of invasions requires understanding why some species fail to establish alien populations,...

Insights into animal behaviour play an increasingly central role in species-focused conservation practice. However, progress towards incorporating behaviour into regional or global conservation strategies has been far more limited, not least because standardised datasets of behavioural traits are generally lacking at wider taxonomic or spatial scal...

Cranial morphology in birds is thought to be shaped by adaptive evolution for foraging performance. This understanding of ecomorphological evolution is supported by observations of avian island radiations, such as Darwin's finches, which display rapid evolution of skull shape in response to food resource availability and a strong fit between crania...

Table S1. Parameter values explored in the simulations.

Aim Accelerating rates of anthropogenic introductions are leading to a dramatic restructuring of species distributions globally. However, the extent to which invasions alter the imprint of evolutionary history in species geographical ranges remains unclear. Here, we provide a global assessment of how the introduction, establishment and spread of al...

Ecological communities are assembled from the overlapping of species in geographic space, but the mechanisms facilitating or limiting such overlaps are difficult to resolve. Here, we combine phylogenetic, morphological and environmental data to model how multiple processes regulate the origin and maintenance of geographic range overlap across 1,115...

The role of ecological limits in regulating the distribution and diversification of species remains controversial. Although such limits must ultimately arise from constraints on local species coexistence, this spatial context is missing from most macroevolutionary models. Here, we develop a stochastic, spatially explicit model of species diversific...

Aim: To identify the factors that influence the availability of data on the negative impacts of alien bird species, in order to understand why more than 70% are currently classified as Data Deficient (DD) by the Environmental Impact Classification of Alien Taxa (EICAT) protocol. Location: Global. Methods: Information on factors hypothesised to infl...

Identifying the factors that determine the success of biological invasions has major consequences for both ecological theory and conservation decision-making. Reliably inferring these factors depends on adequately accounting for the known effects of propagule pressure on establishment success, but detailed information on the size and number of intr...

Quantifying the role of biodiversity in ecosystems not only requires understanding the links between species and the ecological functions and services they provide, but also how these factors relate to measurable indices, such as functional traits and phylogenetic diversity. However, these relationships remain poorly understood, especially for hete...

Meeting the ever-increasing needs of the Earth’s human population without excessively reducing biological diversity is one of the greatest challenges facing humanity, suggesting that newapproaches to biodiversity conservation are required. One idea rapidly gaining momentum-as well as opposition-is to incorporate the values of biodiversity into deci...

The association between species richness and ecosystem energy availability is one of the major geographic trends in biodiversity. It is often explained in terms of energetic constraints, such that coexistence among competing species is limited in low productivity environments. However, it has proven challenging to reject alternative views, includin...

Geographical variation in sister species richness across grid cells (n = 10,938 cells). (A) The relationship between the richness of all sister species in the analysis (n = 1,021 x 2 species) and the total richness of all bird species (n = 9,993 species). (B) The relationship between the richness of locally coexisting sister species and the richnes...

Simulation tests of model reliability and precision. (DOCX)

Examples of geographic isolation (allopatry; unfilled squares) and coexistence (sympatry; grey diagonal lines) between sister species of African Bee-eaters (Merops). In (A), sister species are completely spatially segregated; in (B), sister species coexist but are allopatric in some parts of their range. Insets show the distribution of NPP values a...

Predictors of species coexistence across pairs (n = 1,021 pairs) and within pairs (n = 187 pairs) for the posterior distribution of trees. Results are shown for both univariate and multivariate models and for all four range overlap thresholds (5%, 20%, 50%, 80%) used to define coexistence. (DOCX)

Reliability of estimates of the transition rate from allopatry to sympatry (σ, top panel) and from sympatry to allopatry (ε, bottom panel) for different species ages (mean age = 1.5, 3.3, and 10 Ma). Colours denote the values of σ and ε used in the simulation. Box plots show the spread of estimated values from 100 replicate simulations and lines th...

Model parameter estimates for the Null and energy-availability dependent (EAD) model of coexistence dynamics (n = 1,021 pairs). Hazard ratios indicate the relative change in the transition rate to coexistence (σ) and segregation (ε) between minimum and maximum NPP. (DOCX)

The distribution of extant sister species pairs across the avian evolutionary tree, highlighting pairs that are currently in geographic isolation (blue) or coexistence (red). Results are shown for a single tree from the posterior distribution and including only species containing genetic data (6,670 species). Our analyses were run over a total of 1...

Predictors of species coexistence across pairs (n = 1,028 pairs) for the maximum clade credibility (MCC) tree. Results are shown for both univariate and multivariate models and for all four range overlap thresholds (5%, 20%, 50%, 80%) used to define coexistence. (DOCX)

Predictors of species coexistence across pairs (n = 1,021 pairs) for models including both NPP and temperature seasonality. Results are shown for both univariate and multivariate models and for all four range overlap thresholds (5%, 20%, 50%, 80%) used to define coexistence. (DOCX)

Multipredictor phylogenetic mixed models of species coexistence (n = 1,021 pairs) fitted across the posterior distribution of trees. (DOCX)

Model parameter estimates for the Null and latitudinal dependent (LD) model of coexistence dynamics fit to all (“Global;” n = 1,021 pairs) and New World (n = 492 pairs) sisters. Hazard ratios indicate the relative change in the transition rate to coexistence (σ) and segregation (ε) between minimum and maximum absolute geographic latitude. (DOCX)

The relationship between total avian species richness (n = 9,993 species) and sister species coexistence (percentage; n = 1,021 pairs) accounting for biogeographic realm (n = 8,471 cells). Effect sizes show contrasts to the Australian realm. (DOCX)

Slow-downs in lineage accumulation in phylogenies suggest that speciation rates decline as diversity increases. Likelihood methods have been developed to detect such diversity-dependence. However, a thorough test of whether such approaches correctly infer diversity-dependence is lacking. Here we simulate phylogenetic branching under linear negative...

Variation in species richness across environmental gradients may be associated with an expanded volume or increased packing of ecological niche space. However, the relative importance of these alternative scenarios remains unknown, largely because standardized information on functional traits and their ecological relevance is lacking for major dive...

Quantifying the role of biodiversity in ecosystems not only requires understanding the links between species and the ecological functions and services they provide, but also how these factors relate to measurable indices, such as functional traits and phylogenetic diversity. However, these relationships remain poorly understood, especially for hete...

Quantifying the role of biodiversity in ecosystems not only requires understanding the links between species and the ecological functions and services they provide, but also how these factors relate to measurable indices, such as functional traits and phylogenetic diversity. However, these relationships remain poorly understood, especially for hete...

Key future research questions underpinning understanding of the values of biodiversity

Key future research questions underpinning understanding of the values of biodiversity

Key future research questions underpinning understanding of the values of biodiversity

Balancing the ever-increasing needs of the Earth's human population with the maintenance of the biological diversity that ultimately supplies those needs is one of the greatest challenges facing humanity. The scale of this challenge has led to suggestions that a new approach to biodiversity conservation is needed. One idea rapidly gaining momentum—...

Under allopatric speciation models, a key step in the build-up of species richness is population dispersal leading to the co-occurrence of previously geographically isolated forms. Despite its central importance for community assembly, the extent to which the transition from spatial segregation (allopatry or parapatry) to coexistence (sympatry) is...

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 exti...

Whether biotic interactions limit geographic ranges has long been controversial, and traditional analyses of static distribution patterns have made little progress towards resolving this debate. Here, we use a novel phylogenetic approach to test whether biotic interactions constrain the transition to secondary sympatry following speciation. Applyin...

While the geographic range of a species is a fundamental unit of macroecology and a leading predictor of extinction risk, the evolutionary dynamics of species' ranges remain poorly understood. Based on statistical associations between range size and species age, many studies have claimed support for general models of range evolution in which the ar...

Phylogenetic trees often depart from the expectations of stochastic models, exhibiting imbalance in diversification among lineages and slowdowns in the rate of lineage accumulation through time. Such departures have led to a widespread perception that ecological differences among species or adaptation and subsequent niche filling are required to ex...

Ecology Letters (2010) 13: 705–715 The environmental factors limiting species’ ranges across broad geographic and taxonomic scales are central to questions regarding the geographic variation in biodiversity and impacts of environmental change. However, our understanding remains relatively limited owing to the small-scale, correlative nature of most...

The invasion of alien trees is a major threat to the freshwater resources and biodiversity of South Africa. The Working for Water (WfW) Program was initiated in 1995 in order to control the growth and spread of woody alien species in riparian zones, but the extent to which the indigenous vegetation naturally recovers following alien clearance remai...

There is growing evidence that distance- and density-dependent recruitment are important factors in structuring tree communities in temperate forests. Although pathogens have generally been assumed to be driving these patterns, few studies have attempted to experimentally identify the agent responsible. Here we investigate patterns of recruitment i...