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- Threatened and extinct island endemic birds of the world: Distribution, threats and functional diversityPublication . Matthews, Thomas J.; Wayman, Joseph P.; Cardoso, Pedro; Sayol, Ferran; Hume, Julian P.; Ulrich, Werner; Tobias, Joseph A.; Soares, Filipa C.; Thébaud, Christophe; Martin, Thomas E.; Triantis, Kostas A.AIM: The world's islands support disproportionate levels of endemic avian biodiversity despite suffering numerous extinctions. While intensive recent research has focused on island bird conservation or extinction, few global syntheses have considered these factors together from the perspective of morphological trait diversity. Here, we provide a global summary of the status and ecology of extant and extinct island birds, the threats they face and the implications of species loss for island functional diversity. LOCATION: Global. TAXON: Birds. METHODS: We provide a review of the literature on threatened and extinct island birds, with a particular focus on global studies that have incorporated functional diversity. Alongside this, we analyse IUCN Red List data in relation to distribution, threats and taxonomy. Using null models and functional hypervolumes, in combination with morphological trait data, we assess the functional diversity represented by threatened and extinct island endemic birds. RESULTS AND MAIN CONCLUSIONS: We find that almost half of all island endemic birds extant in 1500 CE are currently either extinct or threatened with extinction, with the majority of threatened extant species having declining population trends. We also found evidence of 66 island endemic subspecies extinctions. The primary threats to extant island endemic birds currently are agriculture, biological resource use, and invasive species. While there is overlap between the hotspots of threatened and extinct island endemics birds, there are some notable differences, including the Philippines and Indonesia, which support a substantial number of threatened species but have no recorded post-1500 CE bird extinctions. Traits associated with threatened island endemic birds are large body mass, flightlessness, aquatic predator, omnivorous and vertivorous trophic niches, marine habitat affinity, and, paradoxically, higher dispersal ability. Critically, we find that threatened endemics (i) occupy distinct areas of beak morphospace, and (ii) represent substantial unique areas of the overall functional space of island endemics. We caution that the loss of threatened species may have severe effects on the ecological functions birds provide on islands.
- Species–area relationships in continuous vegetation : Evidence from Palaearctic grasslandsPublication . Dengler, Jürgen; Matthews, Thomas J.; Steinbauer, Manuel J.; Wolfrum, Sebastian; Boch, Steffen; Chiarucci, Alessandro; Conradi, Timo; Dembicz, Iwona; Marcenò, Corrado; García‐Mijangos, Itziar; Nowak, Arkadiusz; Storch, David; Ulrich, Werner; Campos, Juan Antonio; Cancellieri, Laura; Carboni, Marta; Ciaschetti, Giampiero; De Frenne, Pieter; Dolezal, Jiri; Dolnik, Christian; Essl, Franz; Fantinato, Edy; Filibeck, Goffredo; Grytnes, John‐Arvid; Guarino, Riccardo; Güler, Behlül; Janišová, Monika; Klichowska, Ewelina; Kozub, Łukasz; Kuzemko, Anna; Manthey, Michael; Mimet, Anne; Naqinezhad, Alireza; Pedersen, Christian; Peet, Robert K.; Pellissier, Vincent; Pielech, Remigiusz; Potenza, Giovanna; Rosati, Leonardo; Terzi, Massimo; Valkó, Orsolya; Vynokurov, Denys; White, Hannah; Winkler, Manuela; Biurrun, IdoiaAIM: Species-area relationships (SARs) are fundamental scaling laws in ecology although their shape is still disputed. At larger areas, power laws best represent SARs. Yet, it remains unclear whether SARs follow other shapes at finer spatial grains in continuous vegetation. We asked which function describes SARs best at small grains and explored how sampling methodology or the environment influence SAR shape. Location Palaearctic grasslands and other non-forested habitats. TAXA: Vascular plants, bryophytes and lichens. METHODS: We used the GrassPlot database, containing standardized vegetation-plot data from vascular plants, bryophytes and lichens spanning a wide range of grassland types throughout the Palaearctic and including 2,057 nested-plot series with at least seven grain sizes ranging from 1 cm(2) to 1,024 m(2). Using nonlinear regression, we assessed the appropriateness of different SAR functions (power, power quadratic, power breakpoint, logarithmic, Michaelis-Menten). Based on AICc, we tested whether the ranking of functions differed among taxonomic groups, methodological settings, biomes or vegetation types. RESULTS: The power function was the most suitable function across the studied taxonomic groups. The superiority of this function increased from lichens to bryophytes to vascular plants to all three taxonomic groups together. The sampling method was highly influential as rooted presence sampling decreased the performance of the power function. By contrast, biome and vegetation type had practically no influence on the superiority of the power law. MAIN CONCLUSIONS: We conclude that SARs of sessile organisms at smaller spatial grains are best approximated by a power function. This coincides with several other comprehensive studies of SARs at different grain sizes and for different taxa, thus supporting the general appropriateness of the power function for modelling species diversity over a wide range of grain sizes. The poor performance of the Michaelis-Menten function demonstrates that richness within plant communities generally does not approach any saturation, thus calling into question the concept of minimal area.
- Environmental drivers and spatial scaling of species abundance distributions in Palaearctic grassland vegetationPublication . Ulrich, Werner; Matthews, Thomas J.; Biurrun, Idoia; Campos, Juan Antonio; Czortek, Patryk; Dembicz, Iwona; Essl, Franz; Filibeck, Goffredo; del Galdo, Gian‐Pietro Giusso; Güler, Behlül; Naqinezhad, Alireza; Török, Péter; Dengler, JürgenSpecies abundance distributions (SADs) link species richness with species abundances and are an important tool in the quantitative analysis of ecological communities. Niche-based and sample-based SAD models predict different spatial scaling properties of SAD parameters. However, empirical research on SAD scaling properties is largely missing. Here we extracted percentage cover values of all occurring vascular plants as proxies of their abundance in 1725 10-m2 plots from the GrassPlot database, covering 47 regional data sets of 19 different grasslands and other open vegetation types of the Palaearctic biogeographic realm. For each plot, we fitted the Weibull distribution, a model that is able to effectively mimic other distributions like the log-series and lognormal, to the species–log abundance rank order distribution. We calculated the skewness and kurtosis of the empirical distributions and linked these moments, along with the shape and scale parameters of the Weibull distribution, to plot climatic and soil characteristics. The Weibull distribution provided excellent fits to grassland plant communities and identified four basic types of communities characterized by different degrees of dominance. Shape and scale parameter values of local communities on poorer soils were largely in accordance with log-series distributions. Proportions of subdominant species tended to be lower than predicted by the standard lognormal SAD. Successive accumulation of plots of the same vegetation type yielded nonlinear spatial scaling of SAD moments and Weibull parameters. This scaling was largely independent of environmental correlates and geographic plot position. Our findings caution against simple generalizations about the mechanisms that generate SADs. We argue that in grasslands, lognormal-type SADs tend to prevail within a wider range of environmental conditions, including more extreme habitats such as arid environments. In contrast, log-series distributions are mainly restricted to comparatively species-rich communities on humid and fertile soils.
- Unravelling the small‐island effect through phylogenetic community ecologyPublication . Matthews, Thomas J.; Rigal, François; Kougioumoutzis, Kostas; Trigas, Panayiotis; Triantis, KonstantinosAIM: The small-island effect (SIE) describes a different relationship between island area and species richness on smaller compared to larger islands. The pattern has recently gained widespread support. However, few studies have attempted to identify the actual mechanisms driving the SIE. Here, we use a phylogenetic community framework to study the SIE, based on the assumption that if the dominant assembly processes differ between small and large islands, patterns of phylogenetic community structure should shift across the area and habitat diversity gradient. LOCATION: The Aegean Archipelago, Greece. TAXON: Plants. METHODS: We used a large dataset of 3,262 vascular plant species distributed across 173 islands, in combination with a species-level phylogeny. The phylogenetic community structure of each island was calculated using a null modelling framework and was quantified using effect sizes (ES); negative values indicating phylogenetic clustering and positive values overdispersion. Habitat diversity, species richness, phylogenetic diversity (PD) and ES values were regressed against log10-transformed area and we tested for a SIE using piecewise regression models. We also assessed differences in taxonomic and phylogenetic composition between small and large islands using a beta diversity framework. RESULTS: We found evidence of a SIE using species richness, PD and phylogenetic community structure (ES values). Small islands displayed low variation in habitat diversity and tended to be more phylogenetically clustered, while large islands shifted from phylogenetic clustering towards phylogenetic overdispersion with increasing area and habitat diversity. In addition, we showed that phylogenetic composition tended to be more similar between small islands than expected. MAIN CONCLUSION: Overall, our results provide an example of a SIE in the analysis of island phylogenetic community structure, and point to a role of habitat diversity in driving the SIE more generally.
- Impact of human foraging on tree diversity, composition, and abundance in a tropical rainforestPublication . Asuk, Sijeh A.; Matthews, Thomas J.; Sadler, Jonathan P.; Pugh, Thomas A. M.; Ebu, Vincent T.; Ifebueme, Nzube M.; Kettridge, NicholasTropical forest tree communities are structured by a range of large-scale drivers including elevation, certain high-impact anthropogenic activities (e.g., deforestation), and fires. However, low-impact human activities such as foraging may also be subtly but notably altering the composition of tropical forest tree communities. The study assessed the (i) differences in species diversity, patterns of relative abundance, and pairwise beta diversity between trees with edible and inedible fruits and seeds along an elevation gradient, and (ii) impact of human foraging on the forest tree communities in Oban Division of Cross River National Park, Nigeria. Fifteen permanent 40 by 40 m plots were established along an elevational gradient (120–460 m above mean sea level). All trees of 0.1 m diameter at breast height (dbh) and above were measured, identified, and, with the aid of structured questionnaires, classified into those with edible and inedible fruits/seeds. A total of 35 edible species with density of 128 stems/hectare and basal area of 11.99 m2/hectare, and 109 inedible species with density of 364 stems/hectare and basal area of 22.42 m2/hectare were sampled. However, the evenness of edible and inedible species was similar at pooled and plot levels. For inedible species, there was a positive relationship between pairwise beta diversity and elevation, and this was driven mainly by turnover. In contrast, edible species exhibited a non-significant trend between elevation and beta diversity. Thus, the study showed that human foraging of edible fruits may have subtly influenced patterns of species diversity and community structure in this tropical forest.
- Environmental filtering underpins the island species : area relationship in a subtropical anthropogenic archipelagoPublication . Liu, Jinliang; Matthews, Thomas J.; Zhong, Lei; Liu, Jiajia; Wu, Donghao; Yu, MingjianNumerous mechanisms have been proposed to explain the island species-area relationship (ISAR), including the passive sampling effect, the habitat diversity effect, ecological drift and a group of mechanisms jointly termed environmental filtering (or abiotic selection process). However, determining which of these hypotheses underpins the ISAR in a given system remains an open and controversial question, particularly with regards to the environmental filtering. The effect of environmental filtering on the ISAR for woody plants was tested on 29 islands in a subtropical land-bridge archipelago. Island area had a significant effect on species richness, while isolation was not found to have an effect. After controlling for the passive sampling effect and habitat diversity using a systematic sampling design, we found that a positive ISAR remained. After controlling for island area and isolation, species richness was significantly affected by environmental conditions (e.g. total phosphorus, soil depth and bulk density). When a null model was used that randomly assigned individuals to islands from the regional pool, the difference between the observed and expected richness was greater for smaller islands relative to larger islands. Synthesis. Our results point to an overlooked role of environmental filtering in driving the island species-area relationship (ISAR). Consequently, our study highlights the importance of considering deterministic process in future analyses of the ISAR.
- A global analysis of avian island diversity–area relationships in the AnthropocenePublication . Matthews, Thomas J.; Wayman, Joseph P.; Whittaker, Robert J.; Cardoso, Pedro; Hume, Julian P.; Sayol, Ferran; Proios, Konstantinos; Martin, Thomas E.; Baiser, Benjamin; Borges, Paulo A. V.; Kubota, Yasuhiro; dos Anjos, Luiz; Tobias, Joseph; Soares, Filipa C.; Si, Xingfeng; Ding, Ping; Mendenhall, Chase D.; Sin, Yong Chee Keita; Rheindt, Frank E.; Triantis, Kostas; Guilhaumon, François; Watson, David M.; Brotons, Lluís; Battisti, Corrado; Chu, Osanna; Rigal, FrançoisResearch on island species–area relationships (ISAR) has expanded to incorporate functional (IFDAR) and phylogenetic (IPDAR) diversity. However, relative to the ISAR, we know little about IFDARs and IPDARs, and lack synthetic global analyses of variation in form of these three categories of island diversity–area relationship (IDAR). Here, we undertake the first comparative evaluation of IDARs at the global scale using 51 avian archipelagic data sets representing true and habitat islands. Using null models, we explore how richness-corrected functional and phylogenetic diversity scale with island area. We also provide the largest global assessment of the impacts of species introductions and extinctions on the IDAR. Results show that increasing richness with area is the primary driver of the (non-richness corrected) IPDAR and IFDAR for many data sets. However, for several archipelagos, richness-corrected functional and phylogenetic diversity changes linearly with island area, suggesting that the dominant community assembly processes shift along the island area gradient. We also find that archipelagos with the steepest ISARs exhibit the biggest differences in slope between IDARs, indicating increased functional and phylogenetic redundancy on larger islands in these archipelagos. In several cases introduced species seem to have ‘re-calibrated’ the IDARs such that they resemble the historic period prior to recent extinctions.
- Assessing tropical forest restoration after fire using birds as indicators : An afrotropical case studyPublication . Rurangwa, Marie Laure; Matthews, Thomas J.; Niyigaba, Protais; Tobias, Joseph A.; Whittaker, Robert J.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.
- Fine‐grain beta diversity of Palaearctic grassland vegetationPublication . Dembicz, Iwona; Dengler, Jürgen; Steinbauer, Manuel J.; Matthews, Thomas J.; Bartha, Sándor; Burrascano, Sabina; Chiarucci, Alessandro; Filibeck, Goffredo; Gillet, François; Janišová, Monika; Palpurina, Salza; Storch, David; Ulrich, Werner; Aćić, Svetlana; Boch, Steffen; Campos, Juan Antonio; Cancellieri, Laura; Carboni, Marta; Ciaschetti, Giampiero; Conradi, Timo; De Frenne, Pieter; Dolezal, Jiri; Dolnik, Christian; Essl, Franz; Fantinato, Edy; García‐Mijangos, Itziar; Giusso del Galdo, Gian Pietro; Grytnes, John‐Arvid; Guarino, Riccardo; Güler, Behlül; Kapfer, Jutta; Klichowska, Ewelina; Kozub, Łukasz; Kuzemko, Anna; Löbel, Swantje; Manthey, Michael; Marcenò, Corrado; Mimet, Anne; Naqinezhad, Alireza; Noroozi, Jalil; Nowak, Arkadiusz; Pauli, Harald; Peet, Robert K.; Pellissier, Vincent; Pielech, Remigiusz; Terzi, Massimo; Uğurlu, Emin; Valkó, Orsolya; Vasheniak, Iuliia; Vassilev, Kiril; Vynokurov, Denys; White, Hannah J.; Willner, Wolfgang; Winkler, Manuela; Wolfrum, Sebastian; Zhang, Jinghui; Biurrun, IdoiaQUESTIONS: Which environmental factors influence fine-grain beta diversity of vegetation and do they vary among taxonomic groups? LOCATION: Palaearctic biogeographic realm. METHODS: We extracted 4,654 nested-plot series with at least four different grain sizes between 0.0001 m² and 1,024 m² from the GrassPlot database, covering a wide range of different grassland and other open habitat types. We derived extensive environmental and structural information for these series. For each series and four taxonomic groups (vascular plants, bryophytes, lichens, all), we calculated the slope parameter (z-value) of the power law species–area relationship (SAR), as a beta diversity measure. We tested whether z-values differed among taxonomic groups and with respect to biogeographic gradients (latitude, elevation, macroclimate), ecological (site) characteristics (several stress–productivity, disturbance and heterogeneity measures, including land use) and alpha diversity (c-value of the power law SAR). RESULTS: Mean z-values were highest for lichens, intermediate for vascular plants and lowest for bryophytes. Bivariate regressions of z-values against environmental variables had rather low predictive power (mean R² = 0.07 for vascular plants, less for other taxa). For vascular plants, the strongest predictors of z-values were herb layer cover (negative), elevation (positive), rock and stone cover (positive) and the c-value (U-shaped). All tested metrics related to land use (fertilization, livestock grazing, mowing, burning, decrease in naturalness) led to a decrease in z-values. Other predictors had little or no impact on z-values. The patterns for bryophytes, lichens and all taxa combined were similar but weaker than those for vascular plants. CONCLUSIONS: We conclude that productivity has negative and heterogeneity positive effects on z-values, while the effect of disturbance varies depending on type and intensity. These patterns and the differences among taxonomic groups can be explained via the effects of these drivers on the mean occupancy of species, which is mathematically linked to beta diversity.
- The species–area relationship in ant ecologyPublication . Ohyama, Leo; Holt, Robert D.; Matthews, Thomas J.; Lucky, AndreaAIM: The positive relationship between species richness and area-the species-area relationship (SAR)-is a key principle in ecology. Previous studies show large variation in the SAR across taxa collectively indicating the necessity of a taxon-focused approach to accurately evaluate biodiversity scaling patterns. Ants are ideal for this given their global distribution and role in ecosystem functioning. Using data from insular ant communities, this study quantified and investigated various attributes of ant SARs and reviewed the SAR literature for ant faunas, world-wide, to identify specific areas for improvement. LOCATION: Islands around the world. TAXON: Ants (Hymenoptera: Formicidae). METHODS: We aggregated data on species richness and island characteristics from previous studies on ant SARs to evaluate effects of climate, biogeographic realm, and latitude on slope values from these studies. A multimodel inference approach was used to determine the form of the different SARs, and whether there were any differences between mainland and insular SARs. We also assessed differences between mainland and insular SAR slopes and intercepts. To seek a general slope coefficient for ants, we used a mixed-effect model. Finally, we tested for potential thresholds in the global insular SAR using piecewise regression models. RESULTS: There was a negative relationship between SAR slopes and precipitation in both mainland and insular SARs, while SAR slopes and intercept values were higher in mainland compared to insular systems. Strong evidence of thresholds emerged in the global insular SAR. Finally, a general slope of 0.16 was observed for insular systems, which is lower than found in previous studies. MAIN CONCLUSIONS: A taxon-focused approach proves to showcase unexpected patterns in the SAR. Ant diversity increases faster across area in mainland areas compared to true islands. The influences of climate and biogeographic realms on the ant SAR warrant deeper study. Our review highlights knowledge gaps in the ant SAR that also extend to other taxa, such as the effects of nonnative species on the SAR.
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