110 results found
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, 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
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.
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
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.
Gallagher RV, Falster DS, Maitner BS, et al., 2020, Open Science principles for accelerating trait-based science across the Tree of Life, Nature Ecology and Evolution, Vol: 4, Pages: 294-303, ISSN: 2397-334X
Synthesizing trait observations and knowledge across the Tree of Life remains a grand challenge for biodiversity science. Species traits are widely used in ecological and evolutionary science, and new data and methods have proliferated rapidly. Yet accessing and integrating disparate data sources remains a considerable challenge, slowing progress toward a global synthesis to integrate trait data across organisms. Trait science needs a vision for achieving global integration across all organisms. Here, we outline how the adoption of key Open Science principles-open data, open source and open methods-is transforming trait science, increasing transparency, democratizing access and accelerating global synthesis. To enhance widespread adoption of these principles, we introduce the Open Traits Network (OTN), a global, decentralized community welcoming all researchers and institutions pursuing the collaborative goal of standardizing and integrating trait data across organisms. We demonstrate how adherence to Open Science principles is key to the OTN community and outline five activities that can accelerate the synthesis of trait data across the Tree of Life, thereby facilitating rapid advances to address scientific inquiries and environmental issues. Lessons learned along the path to a global synthesis of trait data will provide a framework for addressing similarly complex data science and informatics challenges.
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.
Schulte to Bühne H, Tobias JA, Durant SM, et al., 2020, Improving Predictions of Climate Change–Land Use Change Interactions, Trends in Ecology and Evolution, ISSN: 0169-5347
© 2020 Elsevier Ltd 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.
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.
Fecchio A, Bell JA, Collins MD, et al., 2018, Diversification by host switching and dispersal shaped the diversity and distribution of avian malaria parasites in Amazonia, Oikos, Vol: 127, Pages: 1233-1242, ISSN: 0030-1299
Understanding how pathogens and parasites diversify through time and space is fundamental to predicting emerging infectious diseases. Here, we use biogeographic, coevolutionary and phylogenetic analyses to describe the origin, diversity, and distribution of avian malaria parasites in the most diverse avifauna on Earth. We first performed phylogenetic analyses using the mitochondrial cytochrome b (cyt b) gene to determine relationships among parasite lineages. Then, we estimated divergence times and reconstructed ancestral areas to uncover how landscape evolution has shaped the diversification of Parahaemoproteus and Plasmodium in Amazonia. Finally, we assessed the coevolutionary patterns of diversification in this host-parasite system to determine how coevolution may have influenced the contemporary diversity of avian malaria parasites and their distribution among Amazonian birds. Biogeographic analysis of 324 haemosporidian parasite lineages recovered from 4178 individual birds provided strong evidence that these parasites readily disperse across major Amazonian rivers and this has occurred with increasing frequency over the last five million years. We also recovered many duplication events within areas of endemism in Amazonia. Cophylogenetic analyses of these blood parasites and their avian hosts support a diversification history dominated by host switching. The ability of avian malaria parasites to disperse geographically and shift among avian hosts has played a major role in their radiation and has shaped the current distribution and diversity of these parasites across Amazonia.
Chapman P, Tobias JA, Edwards DP, et al., 2018, Contrasting impacts of land use change on phylogenetic and functional diversity of tropical forest birds, Journal of Applied Ecology, Vol: 55, Pages: 1604-1614, ISSN: 0021-8901
1. Biodiversity conservation strategies increasingly target maintaining evolutionary history and the resilience of ecosystem function, not just species richness (SR). This has led to the emergence of two metrics commonly proposed as tools for decision making: phylogenetic diversity (PD) and functional diversity (FD). Yet the extent to which they are interchangeable remains poorly understood. 2. We explore shifts in and relationships between FD and PD of bird communities across a disturbance gradient in Borneo, from old-growth tropical forest to oil palm plantation. 3. We show a marked decline in PD, and an increase in phylogenetic mean nearest taxon distance (MNTD) from forest to oil palm, in line with declining SR across the gradient. However, phylogenetic mean pairwise distance (MPD) is constrained by forest logging more than by conversion to oil palm, taking account of SR. 4. The decline in FD across the gradient is less severe than in PD, with all metrics indicating relatively high trait diversity in oil palm despite low SR, although functional redundancy is much reduced. Accounting for SR, levels of functional over- or under-dispersion of bird communities are strongly coupled to habitat disturbance level rather than to any equivalent phylogenetic metric. 5. Policy Implications. We suggest that while phylogenetic diversity (PD) is an improvement on species richness as a proxy for functional diversity (FD), conservation decisions based on PD alone cannot reliably safeguard maximal FD. Thus, PD and FD are related but still complementary. Priority setting exercises should use these metrics in combination to identify conservation targets.
McEntee JP, Tobias JA, Sheard C, et al., 2018, Tempo and timing of ecological trait divergence in bird speciation., Nature Ecology and Evolution, Vol: 2, Pages: 1120-1127, ISSN: 2397-334X
Organismal traits may evolve either gradually or in rapid pulses, but the relative importance of these modes in the generation of species differences is unclear. Additionally, while pulsed evolution is frequently assumed to be associated with speciation events, few studies have explicitly examined how the tempo of trait divergence varies with respect to different geographical phases of speciation, starting with geographic isolation and ending, in many cases, with spatial overlap (sympatry). Here we address these issues by combining divergence time estimates, trait measurements and geographic range data for 952 avian sister species pairs worldwide to examine the tempo and timing of trait divergence in recent speciation events. We show that patterns of divergence in key ecological traits are not gradual, but instead seem to follow a pattern of relative stasis interspersed with evolutionary pulses of varying magnitude. We also find evidence that evolutionary pulses generally precede sympatry, and that greater trait disparity is associated with sympatry. These findings suggest that early pulses of trait divergence promote subsequent transitions to sympatry, rather than occurring after sympatry has been established. Incorporating models with evolutionary pulses of varying magnitude into speciation theory may explain why some species pairs achieve rapid sympatry whereas others undergo prolonged geographical exclusion.
Pigot A, Jetz W, Sheard C, et al., 2018, The macroevolutionary dynamics of species coexistence in birds, Nature Ecology and Evolution, Vol: 2, Pages: 1112-1119, ISSN: 2397-334X
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 pairs of avian sister species globally. We show that coexistence cannot be adequately predicted by either dispersal-assembly (that is, biogeographic) models or niche-assembly models alone. Instead, our results overwhelmingly support an integrated model with different assembly processes dominating at different stages of coexistence. The initial attainment of narrow geographic overlap is dictated by intrinsic dispersal ability and the time available for dispersal, whereas wider coexistence is largely dependent on niche availability, increasing with ecosystem productivity and divergence in niche-related traits, and apparently declining as communities become saturated with species. Furthermore, although coexistence of any individual pair of species is highly stochastic, we find that integrating assembly processes allows broad variation in the incidence and extent of coexistence to be predicted with reasonable accuracy. Our findings demonstrate how phylogenetic data coupled with environmental factors and functional traits can begin to clarify the multi-layered processes shaping the distribution of biodiversity at large spatial scales.
Bovo AAA, Ferraz KMPMB, Magioli M, et al., 2018, Habitat fragmentation narrows the distribution of avian functional traits associated with seed dispersal in tropical forest, Perspectives in Ecology and Conservation, Vol: 16, Pages: 90-96, ISSN: 2530-0644
Land-use change influences biodiversity in non-random ways, affecting some species and functional groups more than others, with potential implications for the loss or degradation of important ecological processes, such as seed dispersal. Here we investigate the effect of patch-size reduction on the composition and functional richness (FRic) of avian communities in Atlantic Forest fragments, focusing on morphological traits associated with seed dispersal in frugivorous birds. We found that FRic of three key traits—hand-wing index, body mass and gape width—decreased with patch size reduction, because species with larger values for morphological traits were lost through local extinction. The relative absence of large-gaped and more-dispersive frugivores in small forest fragments has important implications because these species play a pivotal role in seed dispersal, carrying higher seed loads for longer distances, and consuming larger-sized seeds that cannot be dispersed by smaller-gaped frugivores. Our results highlight the importance of preserving large or interconnected habitat patches, and promoting habitat restoration of cleared areas, to ensure that sufficient avian functional diversity is maintained to supply the full range of seed dispersal services required by tropical forests, both currently and in future.
Howard C, Stephens PA, Tobias JA, et al., 2018, Flight range, fuel load and the impact of climate change on the journeys of migrant birds, PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, Vol: 285, ISSN: 0962-8452
Climate change is predicted to increase migration distances for many migratory species, but the physiological and temporal implications of longer migratory journeys have not been explored. Here, we combine information about species' flight range potential and migratory refuelling requirements to simulate the number of stopovers required and the duration of current migratory journeys for 77 bird species breeding in Europe. Using tracking data, we show that our estimates accord with recorded journey times and stopovers for most species. We then combine projections of altered migratory distances under climate change with models of avian flight to predict future migratory journeys. We find that 37% of migratory journeys undertaken by long-distance migrants will necessitate an additional stopover in future. These greater distances and the increased number of stops will substantially increase overall journey durations of many long-distance migratory species, a factor not currently considered in climate impact studies.
Drury JP, Tobias JA, Burns KJ, et al., 2018, Contrasting impacts of competition on ecological and social trait evolution in songbirds, PLoS Biology, Vol: 16, ISSN: 1544-9173
Competition between closely related species has long been viewed as a powerful selective force that drives trait diversification, thereby generating phenotypic diversity over macroevolutionary timescales. However, although the impact of interspecific competition has been documented in a handful of iconic insular radiations, most previous studies have focused on traits involved in resource use, and few have examined the role of competition across large, continental radiations. Thus, the extent to which broad-scale patterns of phenotypic diversity are shaped by competition remain largely unclear, particularly for social traits. Here, we estimate the effect of competition between interacting lineages by applying new phylogenetic models that account for such interactions to an exceptionally complete dataset of resource-use traits and social signaling traits for the entire radiation of tanagers (Aves, Thraupidae), the largest family of songbirds. We find that interspecific competition strongly influences the evolution of traits involved in resource use, with a weaker effect on plumage signals, and very little effect on song. Our results provide compelling evidence that interspecific exploitative competition contributes to ecological trait diversification among coexisting species, even in a large continental radiation. In comparison, signal traits mediating mate choice and social competition seem to diversify under different evolutionary models, including rapid diversification in the allopatric stage of speciation.
Derryberry EP, Seddon N, Derryberry GE, et al., 2018, Ecological drivers of song evolution in birds: Disentangling the effects of habitat and morphology, Ecology and Evolution, Vol: 8, Pages: 1890-1905, ISSN: 2045-7758
Environmental differences influence the evolutionary divergence of mating signals through selection acting either directly on signal transmission ("sensory drive") or because morphological adaptation to different foraging niches causes divergence in "magic traits" associated with signal production, thus indirectly driving signal evolution. Sensory drive and magic traits both contribute to variation in signal structure, yet we have limited understanding of the relative role of these direct and indirect processes during signal evolution. Using phylogenetic analyses across 276 species of ovenbirds (Aves: Furnariidae), we compared the extent to which song evolution was related to the direct influence of habitat characteristics and the indirect effect of body size and beak size, two potential magic traits in birds. We find that indirect ecological selection, via diversification in putative magic traits, explains variation in temporal, spectral, and performance features of song. Body size influences song frequency, whereas beak size limits temporal and performance components of song. In comparison, direct ecological selection has weaker and more limited effects on song structure. Our results illustrate the importance of considering multiple deterministic processes in the evolution of mating signals.
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