Understanding when lineages diverged is a common inquiry within the field of biogeography and often requires a rate of evolution and a means to calibrate the phylogeny to absolute time. While fossil evidence is the most common means regarding calibration, estimated molecular rates specific to the group in question are not as widespread. Furthermore, geological events can also be employed to calibrate a phylogeny, especially when lineages have a poor fossil record. In this paper, the effectiveness of employing biogeographic hypotheses to overcome a depauperate fossil record is tested in a group of spiders whose evolution is strongly affected by abiotic forces. Using a known biogeographic break, the fit of two competing biogeographic hypotheses (Ancient Vicariance vs. Inland Dispersal) is tested as calibration points for estimating an evolutionary rate and dates elsewhere across the tree. An optimized dataset of ultraconserved element (UCE) phylogenomic loci, which have been shown to be highly informative in mygalomorph spider systematics (i.e., tarantulas and trapdoor spiders), is employed. Hypothesis testing strongly supports Ancient Vicariance over Inland Dispersal, and phylogenetic inferences recover topological patterns predicted by Ancient Vicariance. Significantly, subsequent modeling proposes a novel estimate of ancient vicariance older than that of any other system observed across this biogeographic break. Finally, the modeling proposes divergence estimates among other Antrodiaetus species that correlate with previous hypotheses. This research broadens knowledge of mygalomorph evolutionary rates, answers questions about the evolutionary history of a relatively old lineage of folding-door spiders, Antrodiaetus (Antrodiaetidae, Mygalomorphae), and proposes a novel hypothesis for divergence times in the Pacific Northwest. Highlights The authors estimate a novel evolutionary rate for atypoid spiders. The authors demonstrate the use of a biogeographic calibration point in a testable fashion for divergence dating. The authors identify a surprising ancient divergence in the Pacific Northwest that is older than other divergences observed across a known biogeographic break. The authors find additional evidence of the impact of emerging grassland habitat on promoting the divergence of Nearctic lineages.
The field of biogeography aims to reconcile geological changes with the distribution of biodiversity in space and through time. To this end, we examine how geology and climate have affected the spatio-temporal build-up of avian diversity on New Guinea and surrounding islands with a particular focus on birds-of-paradise. Here, we present a new palaeogeographic framework for the formation of New Guinea and surrounding islands from 35 Ma (mega-annum) to the present. We then use detailed information about sea-level changes and a new dated phylogenetic tree of the birds-of-paradise to elucidate, in a combined integrative approach, how geology and climate changes through time have shaped this group of birds. The new palaeogeographic model also has implications for our understanding of the early evolution of passerine birds and their dispersal out of Australo-Papua, which we discuss here. Using an integrative and iterative interdisciplinary approach that combines geological, climatic and evolutionary data, we elucidate the biogeographical history of species and clades with seemingly enigmatic present-day distributions. Highlights We present a new palaeogeographic framework (35-0 Ma) for the formation of Earth’s largest tropical island, New Guinea and some surrounding islands, including the northern Moluccas. We integrate data from the new palaegeographic model with information on sea-level fluctuations to determine emergence history and water barriers in space and through time. We present a new dated tree of the birds-of-paradise (Aves, Paradisaeidae), based on genomic data. Using an iterative approach, we synthesise information from the new palaeogeographic model, sea-level fluctuations and the dated tree to determine the optimal time for colonisation of islands around New Guinea by the birds-of-paradise. We discuss the importance of the presence of extensive landmasses north of Australia (proto-Papua) for passerine dispersal and evolution out of Australia. It is clear that significant insight can be gained in both biology and geology when their mutualistic potential is unlocked through an integrative approach.
The freshwater fauna of Central Asia is largely composed of widespread Eurasian taxa and shares little overlap with the highly endemic assemblages of Southeast Asia. Here, the first record of the East Asian pond snail Radix plicatula (W. H. Benson, 1842) in Central Asia (northern Tien Shan, Kazakhstan) is reported, extending its known range by approximately 2,200 km. To assess the origin of this population, morphological data, genetic analysis, and species distribution modeling were combined. Phylogenetic analyses place the Tien Shan specimens within the main Radix plicatula lineage, whereas haplotype data reveal unexpectedly high genetic diversity within a geographically restricted area. These results are compatible with two alternative scenarios—a recent introduction and an older colonization event—although the observed genetic diversity appears more consistent with long-term persistence in the region. Species distribution models produced contrasting results depending on background selection. Models with unrestricted backgrounds predicted a range largely confined to East and Southeast Asia, whereas models with spatially constrained backgrounds and land-cover variables indicated substantially broader suitability, including Central Asia. This discrepancy suggests that the present-day distribution of Radix plicatula is not solely determined by climate. Paleoclimatic projections indicate that suitable habitats were more widespread in the past, forming a belt north of the major Asian mountain systems. Together with the molecular evidence, this suggests a scenario of Pleistocene dispersal between Southeast and Central Asia. Highlights An East and Southeast Asian freshwater snail was discovered far beyond its known range in Central Asia. Genetic structure reveals unexpectedly high diversity, favoring an older colonization scenario over a recent introduction. Ecologically realistic models predict a much broader potential range than is currently observed. Paleoclimatic projections suggest past connectivity north of the major Asian mountain systems. Results support the hypothesis of a previously overlooked dispersal pathway linking East and Central Asia.
Inferring how biodiversity is generated and how it responded to past events is fundamental to understanding how biodiversity may respond to future changes. As the largest ubiquitous taxonomic group amongst marine vertebrates, ray-finned fishes (Actinopterygii) represent a good model to understand the generation of biodiversity and the processes that shaped contemporary biogeographic patterns in the sea. Evidence shows that hotspots of marine fish richness and endemism do not always overlap, due to the distinct processes that contribute to them. In the Pacific Ocean, the tropical western region concentrates the highest records of species richness. In contrast, the peripheral oceanic islands are major endemism centres. Although the evolutionary setting for marine fish endemism in parts of the Central Pacific has been described, processes that generate and maintain biodiversity in other peripheral regions remain unknown. The Southwest Pacific (20°S-55°S and 150°E-165°W) spans subtropical, temperate and subantarctic climates, containing major landmasses such as eastern Australia and New Zealand, as well as oceanic islands. Due to its configuration, the region displays unique biogeographic patterns that can improve our understanding of marine biodiversity evolution. Here, we aim to address this topic by reviewing the latest biogeographic investigations that examine the origin, evolution, and processes shaping patterns of marine fish richness and endemism in the Southwest Pacific. We highlight the utility of specific methodological approaches used in previous investigations, including the inference of molecular phylogenies based on fossil data, probabilistic biogeographic modelling and statistical analysis of phylogenetic measures of richness and endemism. We propose a biogeographic scenario where the subtropical islands of the Southwest Pacific act as biodiversity cradles, with mainland Australia representing the main source of endemic lineages. Empirical data highlight the significance of both rare colonisation events and vicariance within formerly widely distributed lineages in shaping endemism patterns and reveal that the processes shaping patterns of endemism and richness differ at local scales. Highlights The Southwest Pacific is a geologically active region that harbours multiple oceanic islands of volcanic origin. Hotspots of marine fish richness are not geographically concordant with endemism centres along New Zealand, with richness peaking north of the North Island of Aotearoa New Zealand. Heightened richness in these locations likely originates from an overlap of fish fauna that includes older, distantly related taxa inhabiting warmer waters in the north and closely-related marine fish taxa in colder latitudes in the south. Within the Southwest Pacific, the subtropical oceanic islands of Lord Howe, Norfolk and Rangitāhua (Kermadec Islands) are characterised by the highest endemism rates in coastal marine ray-finned fishes. The geographic isolation and unique oceanic, subtropical climate of these islands have likely influenced the establishment of endemism.
Insular aquatic habitats have the potential to expand upon current theory by providing alterna/tive perspectives on island biogeographical processes. Here, we investigate whether marine lakes—seawater surrounded by land—show patterns expected for ‘complete’ (e.g., ‘true’ oceanic islands) or ‘habitat’ islands using species, phylogenetic, and functional diversity of fishes. We surveyed 22 locations across three location types: stratified lakes and mixed lakes (i.e., islands) and ocean (i.e., mainland). Stratified lake communities were depauperate in species, and distinct in the proportion of traits related to colonization, environmental persistence, and niche competition; they are akin to ‘complete’ islands. Mixed lake communities had higher species richness and redundancy in traits when compared to stratified lake communities, and substantial turnover in beta diversity of species, lineages, and traits when compared to the mainland ocean communities; they are akin to ‘habitat’ islands. While two categories of marine lakes—stratified and mixed—were defined a priori based on physical structure and roughly correspond to ‘complete’ and ‘habitat’ islands, communities indicate variation within, and possibly a gradation between location types, including overlapping confidence intervals and outlier cases along primary axes of variation. Such gradation in marine lakes may be attributable to the youth and small size of these marine islands (<20 ky and < 0.1 km2) relative to the ‘complete’ islands common to island biogeography theory (predominantly > 1 my and > 1 km2). Marine islands, therefore, may be defined from a biophysical perspective of communities as providing an emerging perspective with the potential to elucidate the community assembly of young islands generally. Highlights Fish communities in stratified lakes are distinguished from mixed lakes and ocean communities by their species, phylogenetic, and functional diversity. Stratified lake communities share attributes of ‘true’ oceanic islands, such as being geographically isolated, species-poor, and potential hotspots of endemism, in contrast to mixed lake communities that exhibit similarities with ‘habitat’ islands, having high connectivity, being relatively species-rich, lacking endemicity, and having trait redundancy. Stratified lakes do not share relationships with area and age as in mature and large islands; instead, they may illustrate the dynamics of small and young islands. Island biogeography theory is relevant beyond classical terrestrial island types; by applying the theory to marine systems, we can better explore the processes shaping young island communities, which are historically understudied. An island may be identified best by how organisms experience and respond to the geographical and environmental conditions.
Distributions of Amazonian plants are poorly known. Here, we analyze to what degree current Amazon-wide species distribution patterns reflect general aspects of the species’ environmental niches, and how distributions may be affected by climate change. Occurrence records from quantitative field surveys were combined with records from the Global Biodiversity Information Facility (GBIF) after verification of taxonomical identifications. The importance of 40 environmental predictors (ranging from bioclimatic to edaphic variables) was assessed for each species separately. Ensemble species distribution models (SDMs) were trained using current bioclimatic variables, and potential range shifts were then modelled by SDMs using bioclimatic variables from future climatic scenarios. Six different distributional types were identified on the basis of the shape and extent of the predicted distributional area and the most important environmental variables in the SDMs. In order of increasing area of occupancy, the types were: Guianan, Andean, southern, circum-Amazonian, bimodal, and widespread. The edaphic niche was an important predictor of distribution for all species, especially for the Andean and bimodal ones, which had high soil base cation optima. All widespread species had low base cation optima, and their most important predictor was climatic. We observed that, of the 18 species, 14 would significantly lose habitat under the medium and extreme future climate scenarios. We suggest that Amazon-wide plant distribution patterns reflect edaphic optima, with species adapted to cation-rich soils generally having the narrowest distributions and species adapted to poor soils, potentially the broadest. Projected climate change will reduce the suitable habitat area, especially for the core rainforest species, while species currently found in the drier southern Amazonia might be able to expand northwards. Highlights We identified six different distributional types for understory ferns (Guianan, Andean, southern, circum-Amazonian, bimodal, and widespread), and since species in each category shared a unique combination of niche properties in relation to soil nutrient availability and climate, these are likely relevant for other plants as well. Soil base cation concentration emerged as an important variable in all the species distribution models, highlighting the importance of reliable soil data for understanding Amazonian plant distributions. Most species (14 out of 18) were predicted to suffer a net loss of habitat by 2080, even with moderate climate change scenarios; 8 would lose more than 50% under the pessimistic scenario even without considering future deforestation. Species of the core rainforest area were predicted to be especially hard hit by climate change; the only species whose habitat was predicted to expand by more than 25% has a southern distribution that currently extends beyond Amazonia to drier biomes.
Calls to ban high seas fishing have long been justified on biodiversity, economic, equity, and carbon mitigation grounds. A new study reports that even under a low emission climate change scenario, approximately 22% of straddling fish stocks may shift out of exclusive economic zones (EEZs) and into international waters by 2030. Here, we suggest that this projected redistribution strengthens the case for a ban because the high seas could serve as a biodiversity refuge for migrating species, prevent inequitable capture of displaced resources by wealthy distant-water fleets (DWF), and avert a carbon-intensive escalation of long-distance fishing.
Amazonian forest fires rarely, if ever, ignite and spread in the absence of humans. The first colonization of people into South America happened in the late Pleistocene, and by 10,000 years ago, humans had introduced fire into a naive landscape. Here we build on previous databases of burned 14C dated archaeological material and 14C dated charcoal fragments retrieved from soils and reconstruct spatiotemporal patterns of fire in Amazonia for the last 10,000 years. We ask whether fire histories are regionally synchronous, and whether major demographic events such as the 'Great Dying' or 'Early abandonment' appear in the fire histories within or between regions. We found that most of the earliest fires occurred in the peripheral areas and spread into central Amazonian forests mostly around 2000-3000 years ago. The frequency and recurrence of burned 14C dated material also showed a two-phase decline over the last 700 years. Most regions show a decrease in fire occurrence ca. 700-500 years ago and then again during the last 400 years when European influence spread across Amazonia. The restructuring of Amazonian pyrogeography over the last 2000 years has likely played a large role in shaping modern forests.
Climate change is reshaping biodiversity, yet it remains challenging to distinguish the respective influences of short-term weather variability and long-term climate trends, particularly with regard to functional diversity. We analysed two long-term monitoring programmes in the Wadden Sea: one surveying breeding birds in spring and early summer and the other surveying waterbirds and waders throughout the year. Analyses were conducted separately for each programme to reflect their seasonal context. Across the East Frisian Islands (1996-2021), we combined standardised counts with ecomorphological traits to quantify species richness and diversity (using the Shannon Index) as well as functional diversity, expressed as standardised effect sizes of functional richness (FRic) and functional dispersion (FDis). We additionally computed mean species contributions for FDis and FRic. First, we estimated island-specific temporal trends in these metrics and then related them to short-term weather variability and long-term climate trends using mixed-effects models. Although taxonomic diversity generally increased over time, functional diversity often decreased, particularly in the case of FDis. This is consistent with functional homogenisation despite taxonomic gains. FDis was dominated by a few abundant taxa, whereas FRic was driven by less abundant species with distinct traits. The associations with environmental predictors varied between monitoring programmes: breeding-bird functional diversity exhibited stronger links with shortterm weather variability, whereas waterbird and wader patterns were more closely linked with long-term climate trends. Overall, these results emphasise the value of trait-based indicators in long-term monitoring and highlight that functional metrics can reveal community restructuring that is not captured by taxonomic metrics alone.
Leposternon polystegum is a fossorial reptile endemic to Brazil, distributed across several biomes. However, the environmental and spatial factors that shape its distribution remain poorly understood. Species distribution models provide useful insights into how different environmental gradients influence the occurrence of subterranean organisms. In this study, we applied fuzzy logic-based favorability models to identify the main environmental and spatial drivers of L. polystegum distribution. We compared the known distribution of the species with climatic, topographic, hydrographic, and spatial predictors to evaluate their relative influence on environmental suitability. The most favorable areas for the species' presence were concentrated in northeastern Brazil, particularly in semiarid regions with moderate elevation, stable humidity, and proximity to large rivers. The models showed good discrimination performance and revealed that temperature and precipitation gradients, along with spatial structure, affect the species' distribution strongly. Variation partitioning analysis further quantified the relative contribution of environmental and spatial components, confirming that both drivers play a significant role in explaining the occurrence patterns. These results indicate that both current environmental conditions and historical constraints may have influenced L. polystegum's range. This approach provides a valuable tool for future studies, incorporating soil properties and serving to guide conservation strategies focused on fossorial biodiversity in South America.
Pollination by wild insects is vital for maintaining ecosystems and food security, but climate change is altering the biogeography of many pollinator species. While progress has been made in assessing climate-driven range shifts using species distribution models (SDMs), most assume all pollinators are functionally equivalent. Here, we introduce a biogeographic approach that integrates Pollen Deposition Effectiveness (PDE), a quantitative metric of species pollination function, with SDMs by summing PDE values of co-occurring pollinators to assess climate-driven changes in both pollinator distributions and their capacity to deliver pollination services. We demonstrate this approach using mango (Mangifera indica) pollinators in South Africa. We identified 61 mango flower visitors, quantified PDE for 38 pollinating species and projected changes in climatically suitable habitat under two climate scenarios (RCP4.5 and RCP8.5) using SDMs. Both species richness and PDE-weighted pollination provision are predicted to decline across core mango-growing regions, alongside substantial species turnover. We find similar spatial patterns of PDE-weighted and unweighted SDMs, indicating high functional redundancy and identify some over-performing pollinators which could be the focus of targeted conservation efforts. We believe this functional approach enhances SDM outputs and provides greater insight for assessing climate change impacts on ecosystem services.
Recent advances in sedimentary ancient DNA (sedaDNA) are transforming palaeoecological research and offer new opportunities to study biodiversity change on islands. We assess the potential of sedaDNA for reconstructing long-term ecological patterns by evaluating current island studies worldwide. We map geographic representation across the floras of 134 archipelagos and islands in relation to the availability of reference data for the P6 loop of trnL (UAA) intron, the most widely used marker in ancient plant DNA metabarcoding. Our analysis highlights substantial geographic and taxonomic biases, with temperate and tropical islands, regions of particularly high biodiversity, remaining comparatively underrepresented both in sedaDNA studies and in species-level DNA reference databases. These patterns identify clear priorities and opportunities for expanding reference libraries and improving the global applicability of sedaDNA approaches. Nevertheless, our database assessment indicates that when taxonomic reference coverage is relatively complete and depositional conditions are favourable, sedaDNA can provide high-resolution species and trait information. This is exemplified by Lake Torfdalsvatn (Iceland), where adequate reference representation and sedaDNA preservation enables clear detection of declines in Betula and Juniperus following Norse settlement and sheep introduction, as well as trait-based shifts toward vegetation adapted to disturbance, increased aridity, and high light conditions. Highlights The use of sedimentary ancient DNA (sedaDNA) is advancing understanding of past ecosystem dynamics. Relatively few sedaDNA studies have been carried out on islands around the world. Although species-level resolution for the P6 Loop used in plant palaeoecology is uneven globally, genus-level coverage offers promising opportunities to expand island sedaDNA studies even across temperate and tropical regions. When reference databases and underlying floras are complete, high-quality data about past ecosystems can be obtained.
Climatic change drastically shapes the ecology and evolution of lineages across landscapes. In mountainous regions, climatic oscillations drive fine-scale biome shifts and modulate habitat availability along elevation gradients, thereby governing population connectivity. Cold-adapted highland lineages with low dispersal capacity are ideal systems for studying the impact of past climates on geographic range shifts and genomic signatures. Here, we focus on the flightless highland species Calosoma (Callisthenes) pentheri endemic to the Western Balkan mountains, which exhibits a disjunct geographic distribution. We predict that glacial and interglacial periods drove allopatry through cycles of isolation and secondary contact, leaving genomic signatures among populations. Using hyRAD museomics combined with a newly sequenced reference genome we generated 10,794 single nucleotide polymorphisms and 2,278 loci to reconstruct the evolutionary history of this lineage. Admixture and phylogenomic analyses demonstrate clear delineation between the two lineages reflecting their distribution across the Western Balkans. Genetic signatures and divergence-time estimates suggest that these two lineages represent distinct species that diverged in the Late Miocene with little interspecific, but occasional intraspecific, admixture since the Pliocene. The diversification of these species in the Balkans was likely driven by isolation in sky island glacial refugia during the Miocene to Pliocene. Subsequent secondary contact during Pleistocene glacial periods may have occurred but did not result in introgression. Climatic oscillations during Quaternary ice ages similarly triggered admixture between populations of each massif. These species display intermediate stages along the speciation continuum, representing a model system for in-depth studies of climate-driven evolution in sky islands.
The reliability of our knowledge on global biodiversity patterns depends on how comprehensively and consistently biodiversity has been documented, a condition still limited by strong spatial and taxonomic biases. Despite their central role in ecology, the reliability of biodiversity patterns has rarely been supported by a quantitative assessment that explicitly evaluate patterns themselves. Here, we focused on information convergence, an indicator that represents a necessary condition for reliability, and developed a framework to assess the convergence of biodiversity knowledge with data accumulation. Using more than 30 million occurrence records from the Ocean Biodiversity Information System (OBIS), we reconstructed temporal sequences of species distributions and evaluated the convergences of three biodiversity dimensions: species richness, latitudinal diversity distribution, and rarity-weighted species richness across 13 marine taxonomic groups. Convergence varied systematically among taxonomic groups and pattern types: species richness and latitudinal diversity distribution patterns generally stabilized with increasing data, whereas rarity-weighted species richness remained inconsistent across all groups. Weak correlations between record density and mapped species richness per grid cell were associated with higher convergence, indicating saturation in species discovery. The persistently low convergence of rarity-weighted species richness highlights major uncertainty in conservation-relevant rarity metrics. By framing biodiversity knowledge through the convergence of mapped patterns, this study offers a novel quantitative perspective for assessing the maturity of global biodiversity information and identifying where structural knowledge gaps persists. The approach provides a generalizable framework to guide data acquisition, model refinement, and conservation assessments.
Introduction: Land-use changes have transformed many Mediterranean ecosystems in ways that can adversely affect ectotherms such as reptiles. Range-edge reptile populations may be especially sensitive to such changes, as their thermoregulatory requirements depend on an interaction between climate and habitat structure. Here, we asked how climate, land use, predation risk and habitat structure affect two potentially interacting lacertid species at their southernmost range edge: the Levant Green Lizard Lacerta media israelica and the Lebanon Lizard Phoenicolacerta laevis. Methods: Between 2016 and 2018, we sampled both species in 272 woodland sites spanning a 120 km geo-climatic gradient in northern Israel. We quantified land cover, habitat characteristics and predation pressure by Cattle Egrets (Bubulcus ibis), a known predator of both species. We modelled species abundance to evaluate the effects of climate, land use, habitat structure, egret predation pressure and the potential effect of L. media on P. laevis. Results: We recorded 158 L. media individuals and 1,162 P. laevis individuals in 16.5% and 77.2% of sites, respectively. L. media abundance was positively associated with wetter conditions and heterogeneous habitats and negatively associated with cattle grazing. In contrast, P. laevis abundance was unaffected by climate, increased with vegetation productivity, but had negative associations with L. media abundance and increasing egret predation pressure. Conclusions: L. media and P. laevis exhibited contrasting responses to climate, land-use, habitat structure and biotic interactions. Therefore, closely-related reptile species sharing a range edge can respond differently to abiotic and biotic conditions, suggesting a need to refine biogeographic expectations.
Efforts to estimate global species richness often rely on species accumulation curves based on the year of species description. However, this approach assumes that description years accurately reflect discovery times. Many of the recently accepted species (in some groups the majority) are, however, resurrected synonyms or subspecies raised to species level rather than de novo discoveries. Their authority years (i.e. years of first description) are therefore often much older than the year of general acceptance at the species level, meaning that the authority years may provide little information on how many species will eventually be accepted within a clade. Here, we highlight the limitations of relying on authority year, by comparing two taxonomic snapshots taken approximately a decade apart for amphibians, birds, and mammals. We consistently find lower estimates of diversity when relying on older taxonomic snapshots. This occurs because using the authority year on average overestimates how long a species has been accepted, which in turn results in an underestimate of the number of unrecorded species. Based on our analysis, we argue that due to the unreliability of authority year, approaches that rely on it are flawed and may provide misleading support for biogeographic or conservation hypotheses. Therefore, we suggest and advocate for alternative methods to reliably estimate the magnitude of undescribed species.
Neotropical montane cloud forests are terrestrial ecosystems characterized by a consistent high humidity from clouds or mist. Geographically, these forests occur along the Andes, Mesoamerica, and the Caribbean mountain ranges. They have a complex biogeographic history, reflected in their great biodiversity, which includes a high proportion of endemic species. Over the last three decades, several studies examining the spatial distributional patterns of different biological groups have provided valuable insights into identifying areas of endemism in these forests. These analyses differ in terms of taxa, inclusion criteria, methods, spatial scales, and operational geographic units, revealing both shared and contrasting results. Based on a comprehensive review and comparative synthesis of previously published biogeographic studies, we compared recent contributions that describe distributional patterns of fungi, plants, mammals, amphibians, birds, and insects restricted to the Neotropical montane cloud forest. We identified seven well-supported areas of endemism and three additional regions as potential areas of endemism, and we provide a list of endemic taxa diagnosing these natural biotic units. The areas of endemism detected in the montane cloud forest of America correspond to their main mountain chains: (1) Northeastern Mexico, (2) Western and Central Mexico (3) Southern Mexico, (4) Eastern Mexico to north-central Nicaragua, (5) Northwestern South America, including the Sierra Nevada de Santa Marta and Serranía de Perijá, (6) Western South America, and (7) Southern Andean Yungas. Each of these regions encompasses different levels of species richness and composition. Comparing areas of endemism across phylogenetically unrelated taxonomic groups enables us to test hypotheses about the shared history of sympatric species. Furthermore, these areas of endemism have important implications for conservation, particularly where regions of high richness across different biological groups overlap. Highlights The quality and quantity of data available for each biological group condition the delimitation of areas of endemism between different taxonomic groups. The factors that influence the delimitation of these areas include the delimitation and taxonomy of species, data gaps or unsampled regions, as well as biogeographic methods and the size unit used to delimit areas of endemism. There is no standard in the parameters for delimiting areas of endemism (grid origin, species score, endemism index, among others) to provide a starting point of comparison. Our review found at least four areas of endemism for the Mesoamerican cloud forest and three areas of endemism for the cloud forest of South America. The overlap among previously reported areas of endemism (using various methods and spatial scales) suggests that these regions harbor a high degree of endemism across different biological groups, including both restricted and shared taxa, indicating a common biogeographic history.
Sundaland's limestone ecosystems are biodiversity hotspots facing increasing threats from habitat fragmentation and human activities. Our study examines the biogeographical patterns of the limestone-obligate land snail genus Plectostoma across Sundaland to identify the drivers of species richness and endemism. Using 771 georeferenced records of 84 species, we delineated 33 bioregion (biogeographical region) areas based on species composition through Infomap Bioregions analysis. We then examined the effects of integrated island biogeography variables (limestone area, number of hills, isolation), MaxEnt-derived climate suitability, and landscape features such as topography and drainage networks on biogeography patterns and species diversity. Bioregion boundaries were best explained by elevation barriers, drainage basins, and river network connectivity, highlighting the importance of geomorphological and hydrological structure over geographic distance. Generalised linear mixed models revealed that larger limestone areas significantly predicted greater species richness than did higher climate suitability. Canonical Correspondence Analysis showed that endemism composition was primarily driven by the number and total area of limestone hills, while hill isolation and broad-scale climate variables played lesser roles. Most species (87%) were restricted to a single bioregion, with over half qualifying as short-range endemics (<10 km distribution range), underscoring strong spatial turnover. These patterns suggest that ancient geological connectivity, followed by progressive karst fragmentation, shaped current diversity. Future phylogenetic and multi-tax-on studies will enhance the understanding of evolutionary processes and conservation strategies in Sundaland's limestone habitats.
The relationship between species body mass and abundance (MAR-SPP) is a fundamental feature of ecosystems, reflecting whether energy is accumulated in few large organisms or dispersed amongst several smaller ones. While larger species are generally less abundant than smaller ones, identifying broad patterns in this relationship-and the mechanisms shaping it-has been hindered by sparse spatial and taxonomic data. Here, we present a global assessment of MAR-SPP as a function of individual body-mass distribution and species richness, each representing how body size influences energy allocation and the ecological opportunity for diversification. Using extensive species abundance datasets, we model global abundances of 12,057 bird and mammal species at a one-degree resolution. This enables localised reconstructions of community structure and detailed examination of body-mass-abundance-richness relationships. We find that increasing ecosystem productivity and human activity are associated with a relative decline in the abundance of small species. This pattern arises because smaller organisms become more diverse, but not proportionally more abundant, effectively diluting individuals across an increasing number of species. Given that basal metabolic rate scales with body mass to the 0.75 power, our findings suggest that larger species, on average, capture more energy than smaller ones - particularly in productive ecosystems - despite general constraints on their energy acquisition and diversification. Our study demonstrates that energy distribution and ecological opportunity independently shape the functional space governing MAR-SPP. It also highlights the disproportionate impact of human activity on large organisms, revealing lasting consequences for the functional organization of ecological communities.
Habitat islands conceptually bridge true islands and habitat patches, adding new perspectives to island biogeographic principles that shape community assembly processes. Despite growing interest, empirical studies are scarce and the drivers of biodiversity in these systems, such as different aspects of island shape, isolation and habitat diversity, remain unclear. Our aim was to assess how biogeographic parameters influence taxonomic, functional, and phylogenetic plant diversity on habitat islands using quartz islands in South Africa as our model system. We conducted floristic surveys on 20 quartz islands in the harsh and arid summer-rainfall region around Pofadder (Nama-Karoo, South Africa) to quantify species richness, functional dispersion, and phylogenetic mean pairwise distance. Via remote sensing, we derived island metrics and evaluated their effects on the diversity metrics, using multivariate regression analysis. We fitted negative binomial generalized linear models for species richness and linear models for functional and phylogenetic diversity. Island area emerged as the strongest predictor of species richness, consistent with island biogeographic theory. Connectivity was a significant predictor for functional dispersion and explained most of the variation. The mean pairwise distance was significantly influenced solely by the area of the nearest neighbour island, although its explanatory power was only moderate. Our findings highlight that different facets of diversity respond distinctively to biogeographic parameters. Integrating taxonomic, functional, and phylogenetic perspectives is therefore essential for a comprehensive understanding of biodiversity patterns on habitat islands and for providing valuable insights for conservation.
