Biology subjects

Pigot, A. L.

Publications and source records attributed to Pigot, A. L..

7 recordsLinked to original sources

bioRxiv2026

Trait misalignment risk in North American forests under climate change

Climate change is expected to alter forest community composition and functioning, with consequences for the ecosystem services forests provide. However, most macroecological projections focus on individual species distributions and offer limited insight into whether entire communities will remain functionally compatible with future climatic conditions. Here we quantify the risk that present-day forest communities will become functionally misaligned with projected climates using a trait-based approach. We analysed forest inventory data from more than 42,000 mature plots across the United States and Canada. For each plot we estimated community-weighted means for 24 functional traits describing leaf economics, hydraulic function, wood structure, abiotic tolerances and symbiotic strategies. We modelled relationships between community functional composition and environmental conditions, and used these relationships to estimate the trait profiles most compatible with projected late-century climates (2080-2100). Trait-environment misalignment (TEM) risk was quantified as the multivariate distance between current community trait composition and the trait profile associated with the projected future climate at each location, accounting for covariance among traits and intraspecific trait variation. Projected climatic conditions favour trait combinations associated with greater hydraulic capacity and reduced cold and shade tolerance. However, the magnitude of functional misalignment varies strongly across space. The highest TEM risk occurs in high-latitude and montane conifer forests across western and central North America, whereas many mid-latitude broadleaf and mixed forests show lower risk because projected climatic changes reinforce existing drought-adapted functional strategies. Critically, high species richness was the strongest predictor of reduced risk, reinforcing the importance of biodiversity in buffering against adverse outcomes. Our results suggest that many forests are projected to experience climatic conditions associated with functional strategies that differ from those characterising the current community. By identifying where the largest functional adjustments are implied, this trait-based framework provides a scalable way to pinpoint forests most likely to experience suboptimal climate conditions and to prioritise monitoring and climate-adapted management.

ecology↗

bioRxiv2025

Temperature and Ultraviolet Radiation Drive Divergent Visible and Near-Infrared Reflectance Patterns in Butterflies

O_LIClimate change poses extreme risks to biodiversity, threatening the ecosystems upon which humanity depends. Understanding the traits that mediate how organisms respond to climatic gradients in space and time will enable better predictions of the taxa and ecological communities most at risk from warming. C_LIO_LIIn insects, colouration influences thermoregulation, but warming responses must be traded off against other selective pressures. We hypothesise that butterfly wing reflectance in visible and near-infrared (NIR) spectra respond differently to temperature and ultraviolet radiation over space and time. We combined existing reflectance data of 97 butterfly species in both NIR and visible wavelengths, with long-term abundance monitoring data of 120 butterfly communities sampled across 1650 m altitude gradients from May to August in two time periods (2004/5 and 2017). C_LIO_LIThe visible and NIR reflectances of butterfly communities showed a non-linear relationship with altitude, with the lowest reflectance (darkest butterflies) at the coolest, highest sites. In contrast, community visible reflectance decreased through the year as temperatures warmed over spring-summer, whereas community NIR reflectance remained constant, revealing divergent responses of reflectance types to seasonal changes. Temperature had opposing effects on visible and NIR reflectance of butterfly communities, where increasing temperature reduced community visible reflectance strongly while increasing community NIR reflectance slightly. C_LIO_LIConsidering the effects on reflectance of shared evolutionary history in a Bayesian hierarchical model for individual species, lighter-coloured (more reflective) species were associated with warmer temperatures - flying later in spring-summer or at lower altitudes. However, instead of decreasing in reflectance through the year and across temperature gradients, species instead became lighter, we expect as a result of a Simpsons paradox. C_LIO_LIThese results emphasise how visible and NIR reflectance wavelength bands mediate butterflies responses to environmental gradients in distinct ways, despite being highly correlated across species. We also show that incorporating phylogeny into trait-environment models is essential; relying on traits alone would lead to incorrect inferences and predictions of taxa most at risk from warming climates. C_LI

ecology↗

bioRxiv2025

Land-use change undermines the stability of avian functional diversity

Land-use change causes widespread shifts in the composition and functional diversity (FD) of species assemblages, yet the impacts on ecosystem resilience remain uncertain. Stability of ecosystem functioning may increase after land-use change because the most sensitive species are removed, leaving more resilient survivors (Balmford, 1996; Clavel et al., 2010; McKinney & Lockwood, 1999). Alternatively, ecosystems may be destabilized if land-use change reduces functional redundancy, accentuating the ecological impacts of further species loss (Fonseca & Ganade, 2001; McCann, 2000). Current evidence is inconclusive, partly because trait data have not been available to quantify functional stability at sufficient scale. Here, we use morphological measurements of 3696 bird species to estimate shifts in functional redundancy following recent anthropogenic land-use change at 1281 sites worldwide, and then assess the sensitivity of these altered assemblages to future species loss. We find that the proportion of disturbance-tolerant species increases after land-use change, but that this does not increase stability. Instead, we show that functional redundancy is reduced and that further species loss will destabilize ecosystem function because relatively few additional extinctions lead to accelerated losses of FD, particularly in trophic groups delivering important ecological services such as seed dispersal and insect predation. Our analyses reveal that land-use change may have major undetected impacts on the stability of key ecological functions, hindering the capacity of natural ecosystems to absorb further declines in functionality caused by ongoing perturbations.

ecology↗

bioRxiv2024

Colonisation lags predict sympatric diversity in birds

Speciation is the ultimate source of biodiversity. However, because most species arise in spatial isolation (allopatry), how speciation shapes patterns of co-occurring (sympatry) species richness remains unclear. Here we examine how the history of past speciation events influences the maximum sympatric species richness attained across passerine bird clades (n = 40 families). Using a phylogenetic model, we infer that the rate at which species assemble in sympatry is extremely slow, and on average millions of years after speciation onset. As a result, having accounted for clade size, sympatric species richness varies substantially across families, being highest in small or ancient clades comprised of older species that have had more time to accumulate in sympatry. While our analysis does not test the ecological or evolutionary processes causing the slow build-up of sympatric assemblages, our results show that speciation history has left an indelible legacy on current species richness patterns.

evolutionary biology↗

bioRxiv2023

Biophysical constraints on avian adaptation and diversification

The capacity of organisms to adapt to vacant niches or changing environments is limited by physical constraints on morphological evolution. Substantial progress has been made in identifying how these constraints shape the form and function of producers (plants), but our understanding of evolutionary limits in consumers (animals) remains highly limited, in part because the requisite data have not been available at sufficient scale. Using morphometric measurements for all birds, we demonstrate that observed variation is highly restricted--both for beak shape and overall body shape--to triangular regions of morphospace with clearly defined boundaries and vertices. By combining morphometric data with new information on physical functions of measured traits, we provide evidence that the extent of avian morphospace is constrained by biophysical trade-offs between three functional objectives (strength, reach and engulfment capacity) that characterize resource acquisition and processing by the beak, and three locomotory modalities (aerial, aquatic and terrestrial) that characterize avian lifestyles. Our results suggest that over avian evolutionary history, trajectories of morphological change trend towards the vertices, with birds evolving from a core of biophysical generalists to biophysical specialists, associated with faster macroevolutionary turnover of lineages at the periphery or morphospace. Our analyses reveal that the structure of avian morphological diversity follows relatively simple rules defined by biophysical constraints and trade-offs, shedding light on the process shaping modern animal diversity and responses to environmental change.

ecology↗

bioRxiv2022

Disentangling the historical routes to community assembly in the global epicentre of biodiversity

AimThe 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 proposed including, (1) the sorting of already elevationally divergent species, (2) the displacement of elevation upon secondary contact, potentially followed by convergence, or (3) elevational conservatism, in which ancestral elevational ranges are retained. However, the relative contribution of these processes to generating patterns of elevational overlap and turnover is unknown. LocationTropical mountains of Central- and South-America. Time periodThe last 12 myr. Major taxa studiedBirds. MethodsWe collate a dataset of 165 avian sister pairs containing estimates of phylogenetic age, geographical and regional elevational range overlap. We develop a framework based on continuous-time Markov models to infer the relative frequency of different historical pathways in explaining present day overlap and turnover of sympatric species along elevational gradients. ResultsWe show that the turnover of closely related bird species across elevation can predominantly be explained by displacement of elevation ranges upon contact (81%) rather than elevational divergence in allopatry (19%). In contrast, overlap along elevation gradients is primarily (88%) explained by conservatism of elevational ranges rather than displacement followed by elevational expansion (12%). Main conclusionsBird communities across tropical elevation gradients are assembled through a mix of processes, including the sorting, displacement and conservatism of species elevation ranges. The dominant role of conservatism in explaining co-occurrence of species on mountain slopes rejects more complex scenarios requiring displacement followed by subsequent expansion. The ability of closely related species to coexist without elevational divergence provides a direct and thus faster pathway to sympatry and may help explain the exceptional species richness of tropical mountains.

evolutionary biology↗

bioRxiv2019

Integrating behaviour and ecology into global biodiversity conservation strategies

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 scales. Here we make use of the recent expansion of global datasets for birds to assess the prospects for including behavioural traits in systematic conservation priority-setting and monitoring programmes. Using IUCN Red List classification for >9500 bird species, we show that the incidence of threat can vary substantially across different behavioural syndromes, and that some types of behaviour--including particular foraging, mating and migration strategies--are significantly more threatened than others. When all factors are included in a combined model, behavioural traits have a weaker effect than well-established geographical and ecological factors, including range size, body mass and human population pressures. We also show that the association between behavior and extinction risk is partly driven by correlations with these underlying factors. Overall, these results suggest that a multi-species approach at the scale of communities, continents and ecosystems can be used to identify and monitor threatened behaviours, and to flag up cases of latent extinction risk, where threatened status may currently be underestimated. Our findings also highlight the importance of comprehensive standardized descriptive data for ecological and behavioural traits, and point the way forward to a deeper integration of behaviour into quantitative conservation assessments.

animal behavior and cognition↗