117 results found
Drury JP, Clavel J, Tobias JA, et al., 2021, Tempo and mode of morphological evolution are decoupled from latitude in birds, PLoS Biology, Vol: 19, ISSN: 1544-9173
The latitudinal diversity gradient is one of the most striking patterns in nature, yet its implications for morphological evolution are poorly understood. In particular, it has been proposed that an increased intensity of species interactions in tropical biota may either promote or constrain trait evolution, but which of these outcomes predominates remains uncertain. Here, we develop tools for fitting phylogenetic models of phenotypic evolution in which the impact of species interactions-namely, competition-can vary across lineages. Deploying these models on a global avian trait dataset to explore differences in trait divergence between tropical and temperate lineages, we find that the effect of latitude on the mode and tempo of morphological evolution is weak and clade- or trait dependent. Our results indicate that species interactions do not disproportionately impact morphological evolution in tropical bird families and question the validity of previously reported patterns of slower trait evolution in the tropics.
Hordley LA, Gillings S, Petchey OL, et al., 2021, Diversity of response and effect traits provides complementary information about avian community dynamics linked to ecological function, Functional Ecology, ISSN: 0269-8463
Functional diversity metrics based on species traits are widely used to investigate ecosystem functioning. In theory, such metrics have different implications depending on whether they are calculated from traits mediating responses to environmental change (response traits) or those regulating function (effect traits), yet trait choice in diversity metrics is rarely scrutinized.Here, we compile effect and response traits for British bird species supplying two key ecological services—seed dispersal and insect predation—to assess the relationship between functional diversity and both mean and stability of community abundance over time.As predicted, functional diversity correlates with stability in community abundance of seed dispersers when calculated using response traits. However, we found a negative relationship between functional diversity and mean community abundance of seed dispersers when calculated using effect traits. Subsequently, when combining all traits together, we found inconsistent results with functional diversity correlating with reduced stability in insectivores, but greater stability in seed dispersers.Our findings suggest that trait choice should be considered more carefully when applying such metrics in ecosystem management.
Rurangwa ML, Aguirre-Gutierrez J, Matthews TJ, et al., 2021, Effects of land-use change on avian taxonomic, functional and phylogenetic diversity in a tropical montane rainforest, Diversity and Distributions: a journal of conservation biogeography, Vol: 27, Pages: 1732-1746, ISSN: 1366-9516
AimAlthough land use change is a leading cause of biodiversity loss worldwide, there is scant information on the extent to which it has affected the structure and composition of bird communities in the Afrotropical region. This study aimed to quantify the effects of habitat transformation on taxonomic, functional and phylogenetic diversity in Afrotropical bird communities.LocationNyungwe landscape, a montane rainforest with adjoining farmland in south-west Rwanda.MethodsData on bird occurrence, abundance and functional traits were collected in 2017/18 using point counts. We also collected data on habitat and morphological traits for all bird species recorded. We quantified bird diversity using a range of metrics, including the inverse Simpson index, functional dispersion and the standardized effect size of mean nearest taxon distance.ResultsIn comparison with primary forest areas, even low levels of land use change altered species composition and reduced species diversity. Although overall functional diversity and phylogenetic diversity were similar across land use types, we found a significant contraction of trophic and locomotory trait structures of bird communities in restored areas and cultivated areas, respectively. Soil moisture, elevation and lower vegetation height were major factors influencing taxonomic, functional and phylogenetic dimensions of bird communities, although their effects varied across these dimensions.Main conclusionsThe sensitivity of forest species to minor habitat disturbance emphasizes the value of conserving primary vegetation. Long-term conservation of bird communities in Afromontane ecosystems requires halting wide-scale destruction of primary forest, promoting vegetation heterogeneity in the ecological restoration of degraded habitats and adopting wildlife-friendly agricultural practices. Our results suggest that monitoring and conservation in these landscapes can be refined using taxonomic, functional and phylogenetic diversity metr
Benitez-Lopez A, Santini L, Gallego-Zamorano J, et al., 2021, The island rule explains consistent patterns of body size evolution in terrestrial vertebrates, Nature Ecology and Evolution, Vol: 5, Pages: 768-+, ISSN: 2397-334X
Island faunas can be characterized by gigantism in small animals and dwarfism in large animals, but the extent to which this so-called ‘island rule’ provides a general explanation for evolutionary trajectories on islands remains contentious. Here we use a phylogenetic meta-analysis to assess patterns and drivers of body size evolution across a global sample of paired island–mainland populations of terrestrial vertebrates. We show that ‘island rule’ effects are widespread in mammals, birds and reptiles, but less evident in amphibians, which mostly tend towards gigantism. We also found that the magnitude of insular dwarfism and gigantism is mediated by climate as well as island size and isolation, with more pronounced effects in smaller, more remote islands for mammals and reptiles. We conclude that the island rule is pervasive across vertebrates, but that the implications for body size evolution are nuanced and depend on an array of context-dependent ecological pressures and environmental conditions.
Neate-Clegg MHC, Jones SE, Tobias JA, et al., 2021, Ecological correlates of elevational range shifts in tropical birds, Frontiers in Ecology and Evolution, Vol: 9, Pages: 1-16, ISSN: 2296-701X
Globally, birds have been shown to respond to climate change by shifting their elevational distributions. This phenomenon is especially prevalent in the tropics, where elevational gradients are often hotspots of diversity and endemism. Empirical evidence has suggested that elevational range shifts are far from uniform across species, varying greatly in the direction (upslope vs. downslope) and rate of change (speed of elevational shift). However, little is known about the drivers of these variable responses to climate change, limiting our ability to accurately project changes in the future. Here, we compile empirical estimates of elevational shift rates (m/yr) for 421 bird species from eight study sites across the tropics. On average, species shifted their mean elevations upslope by 1.63 ± 0.30 m/yr, their upper limits by 1.62 m ± 0.38 m/yr, and their lower limits by 2.81 ± 0.42 m/yr. Upslope shift rates increased in smaller-bodied, less territorial species, whereas larger species were more likely to shift downslope. When considering absolute shift rates, rates were fastest for species with high dispersal ability, low foraging strata, and wide elevational ranges. Our results indicate that elevational shift rates are associated with species’ traits, particularly body size, dispersal ability, and territoriality. However, these effects vary substantially across sites, suggesting that responses of tropical montane bird communities to climate change are complex and best predicted within the local or regional context.
Wayman JP, Sadler JP, Pugh TAM, et al., 2021, Identifying the drivers of spatial taxonomic and functional beta-diversity of British breeding birds, Frontiers in Ecology and Evolution, Vol: 9, Pages: 1-16, ISSN: 2296-701X
Spatial variation in community composition may be driven by a variety of processes, including environmental filtering and dispersal limitation. While work has been conducted on the relative importance of these processes on various taxa and at varying resolutions, tests using high-resolution empirical data across large spatial extents are sparse. Here, we use a dataset on the presence/absence of breeding bird species collected at the 10 km × 10 km scale across the whole of Britain. Pairwise spatial taxonomic and functional beta diversity, and the constituent components of each (turnover and nestedness/richness loss or gain), were calculated alongside two other measures of functional change (mean nearest taxon distance and mean pairwise distance). Predictor variables included climate and land use measures, as well as a measure of elevation, human influence, and habitat diversity. Generalized dissimilarity modeling was used to analyze the contribution of each predictor variable to variation in the different beta diversity metrics. Overall, we found that there was a moderate and unique proportion of the variance explained by geographical distance per se, which could highlight the role of dispersal limitation in community dissimilarity. Climate, land use, and human influence all also contributed to the observed patterns, but a large proportion of the explained variance in beta diversity was shared between these variables and geographical distance. However, both taxonomic nestedness and functional nestedness were uniquely predicted by a combination of land use, human influence, elevation, and climate variables, indicating a key role for environmental filtering. These findings may have important conservation implications in the face of a warming climate and future land use change.
Rurangwa ML, Matthews TJ, Niyigaba P, et al., 2021, Assessing tropical forest restoration after fire using birds as indicators: An afrotropical case study, Forest Ecology and Management, Vol: 483, Pages: 1-15, ISSN: 0378-1127
The necessity to restore rainforest habitats degraded by anthropogenic fires is widely recognized, however, research on restoration approaches has mainly centred on the recovery of forest structural complexity. There is insufficient evidence on the efficacy of restoration methods in the recovery of the faunal diversity and features linked to key ecosystem functions. We assessed the taxonomic diversity and functional trait structure of bird assemblages in undisturbed primary forest and fire-affected habitats undergoing natural regeneration, as well as areas of assisted natural regeneration, in Nyungwe National Park, Rwanda. We compiled bird occurrence data from point-count sampling, and obtained morphological traits for all species in our assemblages using measurements taken from wild birds and museum specimens. We found marked differences in species composition between primary forest habitats and regenerating forest, with similarity increasing over time since perturbation. Taxonomic diversity was higher in primary forest, and similar between the two restoration approaches. Functional diversity was lower in assisted naturally regenerated habitats, although separate analyses within dietary guilds revealed no differences across habitats. Among desired restoration outcomes, tree species diversity was the leading positive driver of avian species diversity, fern coverage exerted negative effects, while canopy cover had a positive but weak influence. Our findings underscore the importance of preventing anthropogenic fires in tropical rainforest since their impacts on ecological processes are not easily reversed, as shown by the lack of improvement in avian diversity metrics under assisted naturally regeneration in relation to natural regeneration. We stress the need to document both floral and faunal recovery in order to aid informed decision-making on restoration methods.
Schulte To Bühne H, Tobias JA, Durant SM, et al., 2021, Improving predictions of climate change-land use change interactions., Trends in Ecology and Evolution, Vol: 36, Pages: 29-38, ISSN: 0169-5347
Climate change and land use change often interact, altering biodiversity in unexpected ways. Research into climate change-land use change (CC-LUC) interactions has so far focused on quantifying biodiversity outcomes, rather than identifying the underlying ecological mechanisms, making it difficult to predict interactions and design appropriate conservation responses. We propose a risk-based framework to further our understanding of CC-LUC interactions. By identifying the factors driving the exposure and vulnerability of biodiversity to land use change, and then examining how these factors are altered by climate change (or vice versa), this framework will allow the effects of different interaction mechanisms to be compared across geographic and ecological contexts, supporting efforts to reduce biodiversity loss from interacting stressors.
Reaney AM, BouchenakKhelladi Y, Tobias JA, et al., 2020, Ecological and morphological determinants of evolutionary diversification in Darwin's finches and their relatives, Ecology and Evolution, Vol: 10, Pages: 14020-14032, ISSN: 2045-7758
Darwin's finches are a classic example of adaptive radiation, a process by which multiple ecologically distinct species rapidly evolve from a single ancestor. Such evolutionary diversification is typically explained by adaptation to new ecological opportunities. However, the ecological diversification of Darwin's finches following their dispersal to Galápagos was not matched on the same archipelago by other lineages of colonizing land birds, which diversified very little in terms of both species number and morphology. To better understand the causes underlying the extraordinary variation in Darwin's finches, we analyze the evolutionary dynamics of speciation and trait diversification in Thraupidae, including Coerebinae (Darwin's finches and relatives) and, their closely related clade, Sporophilinae. For all traits, we observe an early pulse of speciation and morphological diversification followed by prolonged periods of slower steady‐state rates of change. The primary exception is the apparent recent increase in diversification rate in Darwin's finches coupled with highly variable beak morphology, a potential key factor explaining this adaptive radiation. Our observations illustrate how the exploitation of ecological opportunity by contrasting means can produce clades with similarly high diversification rate yet strikingly different degrees of ecological and morphological differentiation.
Tobias JA, Ottenburghs J, Pigot AL, 2020, Avian diversity: speciation, macroevolution, and ecological function, Annual Review of Ecology, Evolution, and Systematics, Vol: 51, Pages: 533-560, ISSN: 1543-592X
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. Deeper insight is now emerging from a recent wave of integrative studies combining comprehensive phylogenetic, environmental, and functional trait data at unprecedented scales. We review these empirical advances and describe how they are reshaping our understanding of global patterns of bird diversity and the processes by which it arises, with implications for avian biogeography and functional ecology. Further expansion and integration of data sets may help to resolve longstanding debates about the evolutionary origins of biodiversity and offer a framework for understanding and predicting the response of ecosystems to environmental change.
Day JJ, Martins FC, Tobias JA, et al., 2020, Contrasting trajectories of morphological diversification on continents and islands in the Afrotropical white‐eye radiation, Journal of Biogeography, Vol: 47, Pages: 2235-2247, ISSN: 0305-0270
AimMorphological and lineage evolution are predicted to follow different patterns in island and mainland radiations. However, the extent to which these geographical contexts influence evolutionary trajectories remains poorly understood, in part because few studies have focused on species‐rich clades colonizing continents and archipelagos over comparable timeframes. Focusing on a diverse songbird clade radiating on the African continent and adjacent islands, we tested whether morphological evolution is best explained by adaptive or non‐adaptive processes, and whether mainland and island lineages evolved to occupy different regions or volumes of morphological space (morphospace).LocationPalaeotropics, with a particular focus on the Afrotropical region.TaxonWhite‐eyes, Zosterops (Aves: Zosteropidae).MethodsWe generated principal component axes from novel trait data for 120 species and combined this information with a comprehensive dated phylogeny. We then analysed the dynamics of trait and lineage diversification using comparative evolutionary methods.ResultsAn early burst and slowdown pattern of lineage accumulation is not mirrored by phenotypic evolution, which instead shows an apparent convergence on particular phenotypes. However, the overall signature of phenotypic convergence is strongly driven by mainland taxa, in which phenotypes appear to be highly constrained within elevational zones, while speciation events are often associated with phenotypic divergence from one body plan to the other after colonization of highland from lowland habitats, or vice versa. By contrast, island lineages have repeatedly explored novel areas of morphospace with patterns of phenotypic divergence generally not distinguishable from a random‐walk model.Main conclusionsDiversification of Zosterops highlights contrasting evolutionary trends and dynamics for continental versus island species. We suggest the different trajectory of evolution in insular lineages arises from reduced species
Hawes JE, Vieira ICG, Magnago LFS, et al., 2020, A large‐scale assessment of plant dispersal mode and seed traits across human‐modified Amazonian forests, Journal of Ecology, Vol: 108, Pages: 1373-1385, ISSN: 0022-0477
Quantifying the impact of habitat disturbance on ecosystem function is critical to understanding and predicting the future of tropical forests. Many studies have examined post‐disturbance changes in animal traits related to mutualistic interactions with plants, but the effect of disturbance on plant traits in diverse forests has received much less attention.Focusing on two study regions in the eastern Brazilian Amazon, we used a trait‐based approach to examine how seed dispersal functionality within tropical plant communities changes across a landscape‐scale gradient of human modification, including both regenerating secondary forests and primary forests disturbed by burning and selective logging.Surveys of 230 forest plots recorded 26,533 live stems from 846 tree species. Using herbarium material and literature, we compiled trait information for each tree species, focusing on dispersal mode and seed size.Disturbance reduced tree diversity and increased the proportion of lower wood density and small‐seeded tree species in study plots. Disturbance also increased the proportion of stems with seeds that are ingested by animals and reduced those dispersed by other mechanisms (e.g. wind). Older secondary forests had functionally similar plant communities to the most heavily disturbed primary forests. Mean seed size and wood density per plot were positively correlated for plant species with seeds ingested by animals.Synthesis. Anthropogenic disturbance has major effects on the seed traits of tree communities, with implications for mutualistic interactions with animals. The important role of animal‐mediated seed dispersal in disturbed and recovering forests highlights the need to avoid defaunation or promote faunal recovery. The changes in mean seed width suggest larger vertebrates hold especially important functional roles in these human‐modified forests. Monitoring fruit and seed traits can provide a valuable indicator of ecosystem condition, emphasizing the importance o
Jones SEI, Tobias JA, Freeman R, et al., 2020, Weak asymmetric interspecific aggression and divergent habitat preferences at an elevational contact zone between tropical songbirds, Ibis, Vol: 162, Pages: 814-826, ISSN: 0019-1019
Closely related tropical bird species often occupy mutually exclusive elevational ranges, but the mechanisms generating and maintaining this pattern remain poorly understood. One hypothesis is that replacement species are segregated by interference competition (e.g. territorial aggression), but the extent to which competition combines with other key factors such as specialization to distinct habitats remains little studied. Using vegetation surveys and reciprocal playback experiments, we explored the dynamics of interspecific aggression between two Nightingale‐Thrushes Catharus sp. in Central America. We show that lower‐elevation Black‐headed Nightingale‐Thrushes Catharus mexicanus are aggressive towards higher‐elevation Ruddy‐capped Nightingale‐Thrushes Catharus frantzii where they meet at contact zones. However, interspecific aggressive responses were weak and unidirectional, and the two species were associated with different habitats. We conclude that the contact zone is maintained and located primarily by habitat selection, and is probably reinforced by interspecific aggression. This has important implications for understanding how montane species will respond to climate change because the pace and extent of range shifts will not depend solely on habitat shifts or interspecific competition, but instead on interactions between these two factors.
Sol D, Trisos C, Múrria C, et al., 2020, The worldwide impact of urbanisation on avian functional diversity, Ecology Letters, Vol: 23, Pages: 962-972, ISSN: 1461-023X
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 environments have substantially different functional composition and 20% less functional diversity on average than surrounding natural habitats. These changes occur without significant decreases in functional dissimilarity between species; instead, they are caused by a decrease in species richness and abundance evenness, leading to declines in functional redundancy. The reconfiguration and decline of native functional diversity in cities are not compensated by the presence of exotic species but are less severe under moderate levels of urbanisation. Thus, urbanisation has substantial negative impacts on functional diversity, potentially resulting in impaired provision of ecosystem services, but these impacts can be reduced by less intensive urbanisation practices.
Sheard C, Neate-Clegg MHC, Alioravainen N, et al., 2020, Ecological drivers of global gradients in avian dispersal inferred from wing morphology, Nature Communications, Vol: 11, ISSN: 2041-1723
An organism's ability to disperse influences many fundamental processes, from speciation and geographical range expansion to community assembly. However, the patterns and underlying drivers of variation in dispersal across species remain unclear, partly because standardised estimates of dispersal ability are rarely available. Here we present a global dataset of avian hand-wing index (HWI), an estimate of wing shape widely adopted as a proxy for dispersal ability in birds. We show that HWI is correlated with geography and ecology across 10,338 (>99%) species, increasing at higher latitudes and with migration, and decreasing with territoriality. After controlling for these effects, the strongest predictor of HWI is temperature variability (seasonality), with secondary effects of diet and habitat type. Finally, we also show that HWI is a strong predictor of geographical range size. Our analyses reveal a prominent latitudinal gradient in HWI shaped by a combination of environmental and behavioural factors, and also provide a global index of avian dispersal ability for use in community ecology, macroecology, and macroevolution.
Hatfield J, Barlow J, Joly CA, et al., 2020, Mediation of area and edge effects by adjacent land use, Conservation Biology, Vol: 34, Pages: 395-404, ISSN: 0888-8892
Habitat loss, fragmentation and degradation have pervasive detrimental effects on tropical forest biodiversity, but the role of the surrounding land use (i.e. matrix) in determining the severity of these impacts remains poorly understood. We surveyed bird species across an interior-edge-matrix gradient to assess the effects of matrix type on biodiversity at 49 different sites with varying levels of landscape fragmentation in the Brazilian Atlantic Forest – a highly threatened biodiversity hotspot. Our findings revealed that both area and edge effects are more pronounced in forest patches bordering pasture matrix, while patches bordering Eucalyptus plantation maintained compositionally similar bird communities between the edge and the interior, in addition to exhibiting reduced effects of patch size. These results suggest that the type of matrix in which forest fragments are situated can explain a substantial amount of the widely-reported variability in biodiversity responses to forest loss and fragmentation.
Echeverri A, Karp DS, Naidoo R, et al., 2020, Can avian functional traits predict cultural ecosystem services?, People and Nature, Vol: 2, Pages: 138-151, ISSN: 2575-8314
The functional trait diversity of species assemblages can predict the provision of ecosystem services such as pollination and carbon sequestration, but it is unclear whether the same trait-based framework can be applied to identify the factors that underpin cultural ecosystem services and disservices.To explore the relationship between traits and the contribution of species to cultural ecosystem services and disservices, we conducted 404 questionnaire surveys with birdwatchers and local residents in Guanacaste, Costa Rica.We used an information–theoretic approach to identify which of 20 functional traits for 199 Costa Rican bird species best predicted their cultural ecosystem service scores related to birdwatching, acoustic aesthetics, education and local identity, as well as disservices (e.g. harm to crops).We found that diet was the most important variable explaining perceptions of cultural ecosystem service and disservice providers. Aesthetic traits such as plumage colour and pattern were important in explaining birdwatching scores. We also found people have a high affinity for forest-affiliated birds.The insight that functional traits can explain variation among cultural perspectives on values derived from birds offers a first step towards a trait-based system for understanding the species attributes that underpin cultural ecosystem services and disservices.
Pigot AL, Sheard C, Miller ET, et al., 2020, Macroevolutionary convergence connects morphological form to ecological function in birds, Nature Ecology and Evolution, Vol: 4, Pages: 230-239, ISSN: 2397-334X
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 nine key morphological traits for >99% bird species to show that avian trophic diversity is described by a trait space with four dimensions. The position of species within this space maps with 70–85% accuracy onto major niche axes, including trophic level, dietary resource type and finer-scale variation in foraging behaviour. Phylogenetic analyses reveal that these form–function associations reflect convergence towards predictable trait combinations, indicating that morphological variation is organized into a limited set of dimensions by evolutionary adaptation. Our results establish the minimum dimensionality required for avian functional traits to predict subtle variation in trophic niches and provide a global framework for exploring the origin, function and conservation of bird diversity.
Kattge J, Bönisch G, Díaz S, et al., 2020, TRY plant trait database - enhanced coverage and open access, Global Change Biology, Vol: 26, Pages: 119-188, ISSN: 1354-1013
Plant traits – the morphological, anatomical, physiological, biochemical and phenological characteristics of plants – determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystems properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits. For example, we have achieved almost nearly complete global coverage of ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by intraspecific variation and trait-environmental relationships; therefore, for many purposes, these traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database requires a coordinated approach to data mobilization and in-situ trait measurements. This can only be achieved in collaboration with other initiatives.
Betts MG, Wolf C, Pfeifer M, et al., 2019, Extinction filters mediate the global effects of habitat fragmentation on animals, Science, Vol: 366, Pages: 1236-1239, ISSN: 0036-8075
Habitat loss is the primary driver of biodiversity decline worldwide, but the effects of fragmentation (the spatial arrangement of remaining habitat) are debated. We tested the hypothesis that forest fragmentation sensitivity-affected by avoidance of habitat edges-should be driven by historical exposure to, and therefore species' evolutionary responses to disturbance. Using a database containing 73 datasets collected worldwide (encompassing 4489 animal species), we found that the proportion of fragmentation-sensitive species was nearly three times as high in regions with low rates of historical disturbance compared with regions with high rates of disturbance (i.e., fires, glaciation, hurricanes, and deforestation). These disturbances coincide with a latitudinal gradient in which sensitivity increases sixfold at low versus high latitudes. We conclude that conservation efforts to limit edges created by fragmentation will be most important in the world's tropical forests.
Freeman BG, Tobias JA, Schluter D, 2019, Behavior influences range limits and patterns of coexistence across an elevational gradient in tropical birds, Ecography: pattern and diversity in ecology, Vol: 42, Pages: 1832-1840, ISSN: 0906-7590
Does competition influence patterns of coexistence between closely related taxa? Here we address this question by analyzing patterns of range overlap between related species of birds (‘sister pairs’) co‐occurring on a tropical elevational gradient. We explicitly contrast the behavioral dimension of interspecific competition (interference competition) with similarity in resource acquisition traits (exploitative competition). Specifically, we ask whether elevational range overlap in 118 sister pairs that live along the Manu Transect in southeastern Peru is predicted by proxies for competition (intraspecific territorial behavior) or niche divergence (beak divergence and divergence times, an estimate of evolutionary age). We find that close relatives that defend year‐round territories tend to live in non‐overlapping elevational distributions, while close relatives that do not defend territories tend to broadly overlap in elevational distribution. In contrast, neither beak divergence nor evolutionary age was associated with patterns of range limitation. We interpret these findings as evidence that behavioral interactions – particularly direct territorial aggression – can be important in setting elevational range limits and preventing coexistence of closely related species, though this depends upon the extent to which intraspecific territorial behavior can be extended to territorial interactions between species. Our results suggest that interference competition can be an important driver of species range limits in diverse assemblages, and thus highlight the importance of considering behavioral dimensions of the niche in macroecological studies.
Habel JC, Tobias JA, Fischer C, 2019, Movement ecology of Afrotropical birds: Functional traits provide complementary insights to species identity, Biotropica, Vol: 51, Pages: 894-902, ISSN: 0006-3606
Effects of anthropogenic activities on habitats and species communities and populations are complex and vary across species depending on their ecological traits. Movement ecology may provide important insights into species’ responses to habitat structures and quality. We investigated how movement behavior across a human‐modified landscape depends on species identity and species traits, with particular focus on habitat specialization, feeding guilds, and dispersal behavior. We tracked 34 individuals of nine Afrotropical bird species during three years in an anthropogenic riparian landscape of East Africa. We investigated whether species’ functional traits predicted their habitat use and movement behavior better than species’ identities. Our results indicate that habitat specialists mainly occur in dense riparian thickets, while habitat generalists do occur in agricultural land. Home‐ranges of omnivorous habitat generalists are larger than of frugivorous and insectivorous generalists and omnivorous and insectivorous specialists. Movement speed was highest in settlement areas for all species, with activity peaks during morning and afternoon for habitat specialists. Our results reveal that functional traits and species identity provide complementary insights into responses of organisms to habitat structures and habitat quality.
Stoddard MC, Sheard C, Akkaynak D, et al., 2019, Evolution of avian egg shape: underlying mechanisms and the importance of taxonomic scale, Ibis, Vol: 161, Pages: 922-925, ISSN: 0019-1019
Santini L, Butchart SHM, Rondinini C, et al., 2019, Applying habitat and population-density models to land-cover time series to inform IUCN red list assessments, Conservation Biology, Vol: 33, Pages: 1084-1093, ISSN: 0888-8892
The IUCN Red List categories and criteria are the most widely used framework for assessing the relative extinction risk of species. The criteria are based on quantitative thresholds relating to the size, trends and structure of species' distributions and populations. However, data on these parameters are sparse and uncertain for many species and unavailable for others, potentially leading to their misclassification, or classification as Data Deficient. Here we propose an approach combining data on land-cover change and species-specific habitat preferences, population abundance and dispersal distance to estimate key parameters (extent of occurrence, maximum area of occupancy, population size and trend, and degree of fragmentation) and hence IUCN Red List categories. We demonstrate the applicability of our approach for non-pelagic birds and terrestrial mammals globally (∼15,000 species), generating predictions fairly consistent with published Red List assessments, but more optimistic overall. We predict 4.2% of species (467 birds and 143 mammals) to be more threatened than currently assessed, and 20.2% of Data Deficient species (10 birds and 114 mammals) to be at risk of extinction. However, incorporating the habitat fragmentation sub-criterion reduced these predictions 1.5-2.3% and 6.4-14.9% (depending on the quantitative definition of fragmentation) of threatened and Data Deficient species respectively, highlighting the need for improved guidance to Red List assessors on applying this aspect of the Red List criteria. Our approach can be used to complement traditional methods of estimating parameters for Red List assessments. Furthermore, it can readily provide an early warning system to identify species potentially warranting changes in their extinction risk category based on periodic updates of land cover information. Given that our method relies on optimistic assumptions about species distribution and abundance, all species predicted to be more at risk than cu
Tobias JA, Pigot AL, 2019, Integrating behaviour and ecology into global biodiversity conservation strategies, Philosophical Transactions of the Royal Society B: Biological Sciences, Vol: 374, Pages: 1-11, ISSN: 0962-8436
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. 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 International Union for Conservation of Nature Red List classifications for more than 9500 bird species, we show that the incidence of threat can vary substantially across different behavioural categories, and that some types of behaviour—including particular foraging, mating and migration strategies—are significantly more threatened than others. The link between behavioural traits and extinction risk is partly driven by correlations with well-established geographical and ecological factors (e.g. range size, body mass, human population pressure), but our models also reveal that behaviour modifies the effect of these factors, helping to explain broad-scale patterns of extinction risk. 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 towards deeper integration of behaviour into quantitative conservation assessments.This article is part of the theme issue ‘Linking behaviour to dynamics of populations and communities: application of novel approaches in behavioural ecology to conservation’.
Kirschel ANG, Seddon N, Tobias JA, 2019, Range-wide spatial mapping reveals convergent character displacement of bird song, Proceedings of the Royal Society B: Biological Sciences, Vol: 286, ISSN: 0962-8452
A long-held view in evolutionary biology is that character displacement generates divergent phenotypes in closely related coexisting species to avoid the costs of hybridization or ecological competition, whereas an alternative possibility is that signals of dominance or aggression may instead converge to facilitate coexistence among ecological competitors. Although this counterintuitive process—termed convergent agonistic character displacement—is supported by recent theoretical and empirical studies, the extent to which it drives spatial patterns of trait evolution at continental scales remains unclear. By modelling the variation in song structure of two ecologically similar species of Hypocnemis antbird across western Amazonia, we show that their territorial signals converge such that trait similarity peaks in the sympatric zone, where intense interspecific territoriality between these taxa has previously been demonstrated. We also use remote sensing data to show that signal convergence is not explained by environmental gradients and is thus unlikely to evolve by sensory drive (i.e. acoustic adaptation to the sound transmission properties of habitats). Our results suggest that agonistic character displacement driven by interspecific competition can generate spatial patterns opposite to those predicted by classic character displacement theory, and highlight the potential role of social selection in shaping geographical variation in signal phenotypes of ecological competitors.
Cannon PG, Gilroy JJ, Tobias JA, et al., 2019, Land-sparing agriculture sustains higher levels of avian functional diversity than land sharing, Global Change Biology, Vol: 25, Pages: 1576-1590, ISSN: 1354-1013
The ecological impacts of meeting rising demands for food production can potentially be mitigated by two competing land-use strategies: off-setting natural habitats through intensification of existing farmland (land sparing), or elevating biodiversity within the agricultural matrix via the integration of 'wildlife-friendly' habitat features (land sharing). However, a key unanswered question is whether sparing or sharing farming would best conserve functional diversity, which can promote ecosystem stability and resilience to future land-use change. Focusing on bird communities in tropical cloud forests of the Colombian Andes, we test the performance of each strategy in conserving functional diversity. We show that multiple components of avian functional diversity in farmland are positively related to the proximity and extent of natural forest. Using landscape and community simulations, we also show that land-sparing agriculture conserves greater functional diversity and predicts higher abundance of species supplying key ecological functions than land sharing, with sharing becoming progressively inferior with increasing isolation from remnant forest. These results suggest low-intensity agriculture is likely to conserve little functional diversity unless large blocks of adjacent natural habitat are protected, consistent with land sparing. To ensure the retention of functionally diverse ecosystems, we urgently need to implement mechanisms for increasing farmland productivity whilst protecting spared land. This article is protected by copyright. All rights reserved.
Mayhew RJ, Tobias JA, Bunnefeld L, et al., 2019, Connectivity with primary forest determines the value of secondary tropical forests for bird conservation, Biotropica, Vol: 51, Pages: 219-233, ISSN: 0006-3606
Species extinctions caused by the destruction and degradation of tropical primary forest may be at least partially mitigated by the expansion of regenerating secondary forest. However, the conservation value of secondary forest remains controversial, and potentially underestimated, since most previous studies have focused on young, single-aged, or isolated stands. Here, we use point-count surveys to compare tropical forest bird communities in 20–120-year-old secondary forest with primary forest stands in central Panama, with varying connectivity between secondary forest sites and extensive primary forest. We found that species richness and other metrics of ecological diversity, as well as the combined population density of all birds, reached a peak in younger (20-year-old) secondary forests and appeared to decline in older secondary forest stands. This counter-intuitive result can be explained by the greater connectivity between younger secondary forests and extensive primary forests at our study site, compared with older secondary forests that are either (a) more isolated or (b) connected to primary forests that are themselves small and isolated. Our results suggest that connectivity with extensive primary forest is a more important determinant of avian species richness and community structure than forest age, and highlight the vital contribution secondary forests can make in conserving tropical bird diversity, so long as extensive primary habitats are adjacent and spatially connected.Abstract in Spanish is available with online material.
Felice RN, Tobias JA, Pigot AL, et al., 2019, Dietary niche and the evolution of cranial morphology in birds, Proceedings of the Royal Society B: Biological Sciences, Vol: 286, ISSN: 1471-2954
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 cranial phenotype and trophic ecology. However, a recent analysis of larger clades has suggested that diet is not necessarily a primary driver of cranial shape and that phylogeny and allometry are more significant factors in skull evolution. We use phenome-scale morphometric data across the breadth of extant bird diversity to test the influence of diet and foraging behaviour in shaping cranial evolution. We demonstrate that these trophic characters are significant but very weak predictors of cranial form at this scale. However, dietary groups exhibit significantly different rates of morphological evolution across multiple cranial regions. Granivores and nectarivores exhibit the highest rates of evolution in the face and cranial vault, whereas terrestrial carnivores evolve the slowest. The basisphenoid, occipital, and jaw joint regions have less extreme differences among dietary groups. These patterns demonstrate that dietary niche shapes the tempo and mode of phenotypic evolution in deep time, despite a weaker than expected form–function relationship across large clades.
Cooney CR, MacGregor HEA, Seddon N, et al., 2018, Multi-modal signal evolution in birds: re-examining a standard proxy for sexual selection, Proceedings of the Royal Society B: Biological Sciences, Vol: 285, ISSN: 1471-2954
Sexual selection is proposed to be an important driver of speciation and phenotypic diversification in animal systems. However, previous phylogenetic tests have produced conflicting results, perhaps because they have focused on a single signalling modality (visual ornaments), whereas sexual selection may act on alternative signalling modalities (e.g. acoustic ornaments). Here, we compile phenotypic data from 259 avian sister species pairs to assess the relationship between visible plumage dichromatism-a standard index of sexual selection in birds-and macroevolutionary divergence in the other major avian signalling modality: song. We find evidence for a strong negative relationship between the degree of plumage dichromatism and divergence in song traits, which remains significant even when accounting for other key factors, including habitat type, ecological divergence and interspecific interactions. This negative relationship is opposite to the pattern expected by a straightforward interpretation of the sexual selection-diversification hypothesis, whereby higher levels of dichromatism indicating strong sexual selection should be related to greater levels of mating signal divergence regardless of signalling modality. Our findings imply a 'trade-off' between the elaboration of visual ornaments and the diversification of acoustic mating signals, and suggest that the effects of sexual selection on diversification can only be determined by considering multiple alternative signalling modalities.
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