136 results found
Rurangwa ML, Niyigaba P, Tobias JA, et al., 2022, Functional and phylogenetic diversity of an agricultural matrix avifauna: The role of habitat heterogeneity in Afrotropical farmland, Ecology and Evolution, Vol: 12, ISSN: 2045-7758
Varied strategies to alleviate the loss of farmland biodiversity have been tested, yet there is still insufficient evidence supporting their effectiveness, especially when considering phylogenetic and functional diversity alongside traditional taxonomic diversity metrics. This conservation challenge is accentuated in the Afrotropics by the rapid agricultural expansion and intensification for the production of cash crops and by a comparative lack of research. In this study, we assessed how farming practices influence avian phylogenetic and functional diversity. We conducted point-count surveys to assess avian diversity in monocultures of tea and mixed crop farming systems surrounding the Nyungwe rainforest in south-west Rwanda, allowing us to investigate the drivers of avian diversity at farm level. Species composition was found to be moderately different between farm types, with mixed crop farms supporting higher phylogenetic diversity than tea plantations. There were no significant seasonal differences in species composition, functional or phylogenetic diversity. Overall, functional diversity did not differ between farm types, but the dispersion of trophic-related traits was significantly higher in mixed crop farms. Both functional and phylogenetic diversity were influenced by floristic diversity, vegetation height, tree number, and elevation to varying degrees. Our results also (i) highlight the role of farmland heterogeneity (e.g., crop species composition, height, and tree cover extent) in encouraging avian functional and phylogenetic diversity in the Afrotropics and (ii) indicate that the generally negative biodiversity impacts of monoculture agriculture can be partially alleviated by extensive agroforestry with an emphasis on indigenous tree species.
Iglesias-Carrasco M, Tobias JA, Duchene DA, 2022, Bird lineages colonizing urban habitats have diversified at high rates across deep time, GLOBAL ECOLOGY AND BIOGEOGRAPHY, Vol: 31, Pages: 1784-1793, ISSN: 1466-822X
Triantis KA, Rigal F, Whittaker RJ, et al., 2022, Deterministic assembly and anthropogenic extinctions drive convergence of island bird communities, GLOBAL ECOLOGY AND BIOGEOGRAPHY, Vol: 31, Pages: 1741-1755, ISSN: 1466-822X
Weeks BC, O'Brien BK, Chu JJ, et al., 2022, Morphological adaptations linked to flight efficiency and aerial lifestyle determine natal dispersal distance in birds, FUNCTIONAL ECOLOGY, Vol: 36, Pages: 1681-1689, ISSN: 0269-8463
Weeks BC, Naeem S, Lasky JR, et al., 2022, Diversity and extinction risk are inversely related at a global scale, ECOLOGY LETTERS, Vol: 25, Pages: 697-707, ISSN: 1461-023X
Tobias JA, 2022, A bird in the hand: global-scale morphological trait datasets open new frontiers of ecology, evolution and ecosystem science, Ecology Letters, Vol: 25, Pages: 573-580, ISSN: 1461-023X
Crouch NMA, Tobias JA, 2022, The causes and ecological context of rapid morphological evolution in birds, ECOLOGY LETTERS, Vol: 25, Pages: 611-623, ISSN: 1461-023X
Stewart PS, Voskamp A, Santini L, et al., 2022, Global impacts of climate change on avian functional diversity, ECOLOGY LETTERS, Vol: 25, Pages: 673-685, ISSN: 1461-023X
Freeman BG, Weeks T, Schluter D, et al., 2022, The latitudinal gradient in rates of evolution for bird beaks, a species interaction trait, Ecology Letters, Vol: 25, Pages: 635-646, ISSN: 1461-023X
Where is evolution fastest? The biotic interactions hypothesis proposes that greater species richness creates more ecological opportunity, driving faster evolution at low latitudes, whereas the ‘empty niches’ hypothesis proposes that ecological opportunity is greater where diversity is low, spurring faster evolution at high latitudes. We tested these contrasting predictions by analysing rates of beak evolution for a global dataset of 1141 avian sister species. Rates of beak size evolution are similar across latitudes, with some evidence that beak shape evolves faster in the temperate zone, consistent with the empty niches hypothesis. The empty niches hypothesis is further supported by a meta-analysis showing that rates of trait evolution and recent speciation are generally faster in the temperate zone, whereas rates of molecular evolution are slightly faster in the tropics. Our results suggest that drivers of evolutionary diversification are either similar across latitudes or more potent in the temperate zone, thus calling into question multiple hypotheses that invoke faster tropical evolution to explain the latitudinal diversity gradient.
McFadden IR, Fritz SA, Zimmermann NE, et al., 2022, Global plant-frugivore trait matching is shaped by climate and biogeographic history, ECOLOGY LETTERS, Vol: 25, Pages: 686-696, ISSN: 1461-023X
Tobias JA, Sheard C, Pigot AL, et al., 2022, AVONET: morphological, ecological and geographical data for all birds, ECOLOGY LETTERS, Vol: 25, Pages: 581-597, ISSN: 1461-023X
Hordley LA, Powney GD, Brereton T, et al., 2022, Developing a national indicator of functional connectivity, Ecological Indicators, Vol: 136, ISSN: 1470-160X
Habitat loss is a significant driver of biodiversity loss, causing fragmentation into small, isolated patches of suitable land cover. This reduces the permeability of landscapes to the movement of individuals and reduces the likelihood of metapopulation persistence. Quantifying functional connectivity, the ability of a focal species to move between resource patches, is therefore essential for conservation management. There is substantial evidence supporting a technique based on ‘population synchrony’- the degree of correlation in time-series of annual population growth rates between different long-term monitoring sites, to provide a measure of functional connectivity. However, synchronised population dynamics are not only driven by the movement of individuals between sites, but also shared environmental conditions which must be accounted for. Here, we use species survey data from over four decades to investigate average levels and temporal trends in population synchrony for 58 British bird and butterfly species. We first show that population synchrony is significantly associated with synchrony in some seasonal climatic variables. Once we accounted for spatiotemporal climatic patterns, we found that synchrony in butterflies declined over time by 71% between 1985 and 2000 but increased by 64% in recent years. Synchrony in birds showed some decline between 1999 and 2005, after which there appears to being recovery, however most species (74%) show no significant overall change in synchrony. Our proposed indicator provides a ‘species-eye-view’ of functional connectivity using widely available abundance data. Developing such indicators of functional connectivity, which can be updated annually, is crucial to improve the effectiveness of land management strategies for conservation under increasing environmental change.
Sol D, Garcia-Porta J, Gonzalez-Lagos C, et al., 2022, A test of Darwin's naturalization conundrum in birds reveals enhanced invasion success in the presence of close relatives, ECOLOGY LETTERS, Vol: 25, Pages: 661-672, ISSN: 1461-023X
Wayman JP, Sadler JP, Pugh TAM, et al., 2022, Assessing taxonomic and functional change in British breeding bird assemblages over time, GLOBAL ECOLOGY AND BIOGEOGRAPHY, Vol: 31, Pages: 925-939, ISSN: 1466-822X
Kirwan GM, Broughton RK, Lees AC, et al., 2022, The ‘Meidum geese’ revisited: Early historical art is not a suitable basis for taxonomic speculation, Journal of Archaeological Science: Reports, Vol: 41, Pages: 1-5, ISSN: 2352-409X
Romilio (2021) used a taxonomic scoring system to compare differences between three species of geese (Anseriformes) depicted in the Chapel of Itet, one of which he speculated might represent an undescribed (presumably now extinct) species. Despite some apparently distinctive features, the depiction has traditionally been associated with the well-known modern species, red-breasted goose (Branta ruficollis). We discuss limitations in applying the Tobias et al. (2010) scoring system to cases such as this, for which it was not designed, and we outline the many pitfalls that must be considered when attempting to identify historical artwork of birds using examples discussed recently in the ornithological literature. We conclude that the illustrations proposed by Romilio to represent a new Branta goose species are within the range of known plumage variation and potential artistic licence for red-breasted goose, and that this very probably is the species upon which the artwork was based. More generally, we caution against applying the Tobias criteria to cases where a series of specimens cannot be measured, and highlight the difficulties of using illustrations to inform taxonomy.
Leimberger KG, Dalsgaard B, Tobias JA, et al., 2022, The evolution, ecology, and conservation of hummingbirds and their interactions with flowering plants, Biological Reviews, Vol: 97, ISSN: 1464-7931
The ecological co-dependency between plants and hummingbirds is a classic example of a mutualistic interaction: hummingbirds rely on floral nectar to fuel their rapid metabolisms, and more than 7000 plant species rely on hummingbirds for pollination. However, threats to hummingbirds are mounting, with 10% of 366 species considered globally threatened and 60% in decline. Despite the important ecological implications of these population declines, no recent review has examined plant–hummingbird interactions in the wider context of their evolution, ecology, and conservation. To provide this overview, we (i) assess the extent to which plants and hummingbirds have coevolved over millions of years, (ii) examine the mechanisms underlying plant–hummingbird interaction frequencies and hummingbird specialization, (iii) explore the factors driving the decline of hummingbird populations, and (iv) map out directions for future research and conservation. We find that, despite close associations between plants and hummingbirds, acquiring evidence for coevolution (versus one-sided adaptation) is difficult because data on fitness outcomes for both partners are required. Thus, linking plant–hummingbird interactions to plant reproduction is not only a major avenue for future coevolutionary work, but also for studies of interaction networks, which rarely incorporate pollinator effectiveness. Nevertheless, over the past decade, a growing body of literature on plant–hummingbird networks suggests that hummingbirds form relationships with plants primarily based on overlapping phenologies and trait-matching between bill length and flower length. On the other hand, species-level specialization appears to depend primarily on local community context, such as hummingbird abundance and nectar availability. Finally, although hummingbirds are commonly viewed as resilient opportunists that thrive in brushy habitats, we find that range size and forest dependency are key predic
García-Navas V, Tobias JA, Schweizer M, et al., 2021, Trophic niche shifts and phenotypic trait evolution are largely decoupled in Australasian parrots., BMC Ecology and Evolution, Vol: 21, Pages: 1-16, ISSN: 1472-6785
BACKGROUND: Trophic shifts from one dietary niche to another have played major roles in reshaping the evolutionary trajectories of a wide range of vertebrate groups, yet their consequences for morphological disparity and species diversity differ among groups. METHODS: Here, we use phylogenetic comparative methods to examine whether the evolution of nectarivory and other trophic shifts have driven predictable evolutionary pathways in Australasian psittaculid parrots in terms of ecological traits such as body size, beak shape, and dispersal capacity. RESULTS: We found no evidence for an 'early-burst' scenario of lineage or morphological diversification. The best-fitting models indicate that trait evolution in this group is characterized by abrupt phenotypic shifts (evolutionary jumps), with no sign of multiple phenotypic optima correlating with different trophic strategies. Thus, our results point to the existence of weak directional selection and suggest that lineages may be evolving randomly or slowly toward adaptive peaks they have not yet reached. CONCLUSIONS: This study adds to a growing body of evidence indicating that the relationship between avian morphology and feeding ecology may be more complex than usually assumed and highlights the importance of adding more flexible models to the macroevolutionary toolbox.
Sayol F, Cooke RSC, Pigot AL, et al., 2021, Loss of functional diversity through anthropogenic extinctions of island birds is not offset by biotic invasions, Science Advances, Vol: 7, Pages: 1-10, ISSN: 2375-2548
Human impacts reshape ecological communities through the extinction and introduction of species. The combined impact of these factors depends on whether non-native species fill the functional roles of extinct species, thus buffering the loss of functional diversity. This question has been difficult to address, because comprehensive information about past extinctions and their traits is generally lacking. We combine detailed information about extinct, extant, and established alien birds to quantify historical changes in functional diversity across nine oceanic archipelagos. We found that alien species often equal or exceed the number of anthropogenic extinctions yet apparently perform a narrower set of functional roles as current island assemblages have undergone a substantial and ubiquitous net loss in functional diversity and increased functional similarity among assemblages. Our results reveal that the introduction of alien species has not prevented anthropogenic extinctions from reducing and homogenizing the functional diversity of native bird assemblages on oceanic archipelagos.
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, Vol: 35, Pages: 1938-1950, 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.
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.
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.
Tobias JA, Donald PF, Martin RW, et al., 2021, Performance of a points-based scoring system for assessing species limits in birds, Ornithology, Vol: 138, Pages: 1-14, ISSN: 2732-4613
Species are fundamental to biology, conservation, and environmental legislation; yet, there is often disagreement on how and where species limits should be drawn. Even sophisticated molecular methods have limitations, particularly in the context of geographically isolated lineages or inadequate sampling of loci. With extinction rates rising, methods are needed to assess species limits rapidly but robustly. Tobias et al. devised a points-based system to compare phenotypic divergence between taxa against the level of divergence in sympatric species, establishing a threshold to guide taxonomic assessments at a global scale. The method has received a mixed reception. To evaluate its performance, we identified 397 novel taxonomic splits from 328 parent taxa made by application of the criteria (in 2014‒2016) and searched for subsequent publications investigating the same taxa with molecular and/or phenotypic data. Only 71 (18%) novel splits from 60 parent taxa have since been investigated by independent studies, suggesting that publication of splits underpinned by the criteria in 2014–2016 accelerated taxonomic decisions by at least 33 years. In the evaluated cases, independent analyses explicitly or implicitly supported species status in 62 (87.3%) of 71 splits, with the level of support increasing to 97.2% when excluding subsequent studies limited only to molecular data, and reaching 100% when the points-based criteria were applied using recommended sample sizes. Despite the fact that the training set used to calibrate the criteria was heavily weighted toward passerines, splits of passerines and non-passerines received equally strong support from independent research. We conclude that the method provides a useful tool for quantifying phenotypic divergence and fast-tracking robust taxonomic decisions at a global scale.
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
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