High Dispersal Ability Research Articles

Fragmentation shapes nest density and social structure but not genetic diversity of Temnothorax crassispinus (Formicidae)

AbstractHuman activities affect biodiversity by reducing the area of habitats, altering their shape, and increasing their isolation. Ants are particularly sensitive to habitat fragmentation, as it may locally change abiotic conditions, the availability of food and nest sites, the abundance of mutualists, competitors and predators, and also restrict gene flow between patches. As a result, the genetic population and colony structure of ants is expected to show signs of fragmentation. In the present study, we investigated the impact of fragmentation on the ant Temnothorax crassispinus in 45 forest patches across the Franconian Jura, Germany. Based on 283 colonies, of which 156 were genetically analyzed, we evidenced the presence of two putative distinct genetic clusters in the study area. Both the nest densities and the presence of queen were impacted by the number of adjacent forest patches within 400 m around the focal patch, but neither by patch shape nor patch size. We could not detect any effect of fragmentation on the genetic diversity, probably because the high dispersal abilities of T. crassispinus counterbalance any detrimental genetic consequences of fragmentation. Nevertheless, fragmentation still impacts the species density as well as the social structure of its colonies. Further investigations regarding the drivers of occurrence at a finer spatial scale might clarify the role of edge effects on the occurrence of this species.

Heterogeneity in the isolation of patches may be essential for the action of metacommunity mechanisms

The spatial isolation gradient of communities and the gradient in the species dispersal ability are recognized as determinants of biodiversity in metacommunities. In spite of this, mean field models, spatially explicit models, and experiments were mainly focused on idealized spatial arrangements of communities leaving aside the combining role of dispersal and isolation gradients in metacommunity processes. Consequently, we have an incipient understanding of the role of the real spatial arrangement of communities on biodiversity patterns. We focus on six metacommunities for which confident information about the spatial arrangement of water bodies is available. Using coalescent metacommunity models and null models that randomize the location of water bodies, we estimated the potential effect of the landscape on biodiversity and its dependence on species dispersal ability. At extremely low or high dispersal abilities, the location of ponds does not influence diversity because different communities are equally affected by the low or high incoming dispersal. At intermediate dispersal abilities, peripheral communities present a much lower richness and higher beta diversity than central communities. Moreover, metacommunities from real landscapes host more biodiversity than randomized landscapes, a result that is determined by the heterogeneity in the geographic isolation of communities. In a dispersal gradient, mass effects systematically increase the local richness and decrease beta diversity. However, the spatial arrangement of patches only has a large importance in metacommunity processes at intermediate dispersal abilities, which ensures access to central locations but limits dispersal in isolated communities. The ongoing reduction in spatial extent and simplification of the landscape may consequently undermine the metacommunity processes that support biodiversity, something that should be explicitly considered in preserving and restoring strategies.

Diversity of ground-dwelling arthropods on overburden dumps after coal mining

Technogenic landscapes formed by coal mining are unique model sites for studying primary succession. We studied the formation of arthropod communities on rock dumps at coal mine dump sites of different ages and in natural environments. Using the pitfall traps, 5 classes of arthropods were found, with the domination of Insecta and Arachnida. The species composition for most of the studied groups of invertebrates was determined, the Berger-Parker dominance and Shannon species diversity indices were calculated. It has been established that the colonization of dumps depends not only on the age of recultivated lands, but also on habitat conditions (soil characteristics, vegetation parameters). At the beginning of the succession, dumps are massively populated by small-sized species that are tolerant of extreme conditions and have high dispersal abilities. Further development of vegetation entailed a change in the general structure of the ground-dwelling of arthropods communities. Discriminant analysis showed that the macrofauna of the compared sites differs statistically significantly in the space of discriminant functions. The areas at the foot of the dump and the natural biotope are characterized by the maximum differences; the greatest similarity was found between the young and old dumps. A significant contribution to the overall discrimination is made by the beetles of the families Geotrupidae, Staphylinidae, Elateridae, as well as centipedes (Chilopoda), and terrestrial bugs (Hemiptera). This study showed that communities of ground invertebrates are good indicators for monitoring the restoration of technogenically disturbed lands.

Genetic differentiation within species exhibiting widespread gene flow; phylogeography of the downstream-inhabiting speciesEphemera orientalis(Insecta: Ephemeroptera)

AbstractElucidating the mechanism of formation of biota on islands will contribute to our understanding of the evolutionary mechanisms that generate biodiversity. In this study, we focus on the evolutionary history of Ephemera orientalis, which is distributed in East Asia. Phylogenetic analyses were performed using the mitochondrial DNA 16S rRNA, cytochrome oxidase subunit I and the nuclear DNA histone H3 regions. We found that these mayflies exhibit genetic differentiation between the Japanese and Korean populations. The Tsushima population, which is located between the Japanese Islands and the Korean Peninsula, was positioned genetically as a continental clade. The populations of the Fuji-Goko Lakes and Lake Ashino-ko in Central Japan were genetically differentiated from the other populations. The genetic structures over a wide area of the Japanese Islands were confirmed and a loose genetic regionality was observed, which was thought to result from secondary contact of the north-eastern and south-western lineages after their long separation by a geohistorical division event. We have gathered important knowledge regarding the evolutionary history of organisms on islands and investigated the colonization and isolation of biological populations within a species with high dispersal ability.

Genetic diversity and population structure of Capitulum mitella (Linnaeus, 1767) in Fujian (China) revealed by mtDNA COI sequences

Background: Capitulum mitella is a widely distributed and ecologically important stalked barnacle that settles extensively on rocky shores. This species contributes to the structural complexity of intertidal habitats and plays a critical role in the marine ecosystem. This study aimed to reveal the genetic diversity and population structure of C. mitella by analyzing the mitochondrial cytochrome oxidase I (COI) gene. Methods: A 683bp fragment of the COI gene was sequenced from 390 individuals sampled from six localities in Fujian, China. Results: A total of 84 distinct haplotypes were identified through the analysis of 82 polymorphic sites, resulting in an average haplotype diversity (h) of 0.660 and nucleotide diversity (π) of 0.00182. Analysis of molecular variance (AMOVA) and pairwise FST statistics showed no significant population structure. Neutrality tests and mismatch distributions provided evidence of recent population expansion for the species. Conclusions: We suggest that the species' high dispersal ability, and ocean currents coupled with limited physical barriers in the region, contribute to its current phylogeographic structure. These findings enhance our comprehension of the genetic diversity and population structure of C. mitella, providing valuable insights for future conservation efforts.

Population Genetic Structure of the Blue Swimming Crab (Portunus pelagicus) Along the Andaman Sea Coast of Thailand

The blue swimming crab (Portunus pelagicus) is a valuable commercial species. In Thailand, the consumption of the blue swimming crab is increasing. To construct an effective sustainable management plan, genetic information is required. Knowledge of natural stock genetic information can help policymakers design fishing and conservation management policies to maintain genetic diversity. In our study, we examined the genetic structure of the blue swimming crab population on the Andaman Sea coast of Thailand. Partial sequences of the mitochondrial DNA control region (mtDNA CR) with a size of 369-371 base pairs were studied in 150 individuals collected from five sampling sites along Thailand's Andaman Sea coast. Seventy-one haplotypes were characterized by 127 polymorphic sites, indicating high haplotype diversity but low nucleotide diversity across five localities. The multiple tests of population genetic analysis showed a lack of genetic structure. The absence of genetic structure was possibly caused by a high level of gene flow due to the larval blue swimming crab's high dispersal ability. Demographic history findings indicate that the blue swimming crab population has expanded. The findings of our study can be used to guide the management of the blue swimming crab in this region of the Andaman Sea to conserve genetic diversity.

Pelagial Zooplankton Community in a Newly Established Reservoir during and after the Impoundment of a Hydropower Dam

The global increase in energy demand has triggered a global boom in the construction of hydropower dams worldwide affecting biological communities. Our objective is to study the zooplankton (Rotifera, Cladocera and Copepoda) community structure during and after the impoundment of a newly constructed reservoir, to provide valuable knowledge on species diversity, community structure and dynamics to be considered in future management plans. The impoundment period was characterized by increased species richness with high turnover because of the zooplankton’s high dispersal ability and reflected the inoculation of the reservoir with local fauna. Zooplankton during this period were also correlated negatively with depth and positively with total organic nitrogen and nitrate, highlighting the importance of trophic impact. The time following the impoundment reflected the colonization processes to more stable communities. The seasonality domination followed the Mediterranean pattern, with cold and warm periods being differentiated by changes in community structure, while abundance and biomass remained low throughout the studied period. Combined with the dominance of small-sized individuals, it resulted in low grazing pressure, indicating that zooplankton was not the factor controlling phytoplankton.

Dispersal capacity underlies scale-dependent changes in species richness patterns under human disturbance.

Changes in the species richness of (meta-)communities emerge from changes in the relative species abundance distribution (SAD), the total density of individuals, and the amount of spatial aggregation of individuals from the same species. Yet, how human disturbance affects these underlying diversity components at different spatial scales and how this interacts with important species traits, like dispersal capacity, remain poorly understood. Using data of carabid beetle communities along a highly replicated urbanization gradient, we reveal that species richness in urban sites was reduced due to a decline in individual density as well as changes in the SAD at both small and large spatial scales. Changes in these components of species richness were linked to differential responses of groups of species that differ in dispersal capacity. The individual density effect on species richness was due to a drastic 90% reduction of low-dispersal individuals in more urban sites. Conversely, the decrease in species richness due to changes in the SAD at large (i.e., loss of species from the regional pool) and small (i.e., decreased evenness) spatial scales were driven by species with intermediate and high dispersal ability, respectively. These patterns coincide with the expected responses of these dispersal-type assemblages toward human disturbance, namely, (i) loss of low-dispersal species by local extinction processes, (ii) loss of higher-dispersal species from the regional species pool due to decreased habitat diversity, and (iii) dominance of a few highly dispersive species resulting in a decreased evenness. Our results demonstrate that dispersal capacity plays an essential role in determining scale-dependent changes in species richness patterns. Incorporating this information improves our mechanistic insight into how environmental change affects species diversity at different spatial scales, allowing us to better forecast how human disturbance will drive local and regional changes in biodiversity patterns.

Impact of landscape patterns on herb-layer diversity and seed size of Schima superba in urban remnant vegetation: A case study in Guangzhou, Southern China

In order to explore which ecological strategies the remnant vegetation is taken to adapt to urbanization, we investigated three kinds of typical remnant vegetation (grassland, plantation, and secondary forest) in 16 sample sites along the urban–rural gradient in the city of Guangzhou. In this study, we examined plant species composition, and plant diversity, and analyzed the seed of the dominant tree species Schima superba (S. superba) in the secondary forest sites. Those indicators are strongly related with ecological strategies. Eighteen landscape pattern characteristics were determined to reveal the extent of landscape fragmentation. Geographic Information System (GIS), linear regression, and Canonical Correspondence Analysis (CCA) were conducted to analyze the influence of landscape pattern characteristics on plant communities. Results showed that (1) Fragmentation of landscape patterns caused by urbanization has a negative impact on the diversity of herb-layer plants, the dominant species of grassland in the city center are mainly weeds, such as Bidens pilosa and Neyraudia reynaudiana. (2) In order to adapt to the pressure of landscape fragmentation, seeds of S. superba have developed into a larger size, with a competitive advantage over smaller ones. (3) Two different ecological strategies of plant communities adapting to urbanization: The pioneer weeds in grasslands, with high reproductive and dispersal ability, have adopted a r-selection strategy and the dominant tree species with higher survival rates, larger individuals, and longer life spans, have adopted a K-selection strategy to resist disturbance, as well as with a larger seed size to increase viability and settlement ability.

Out of the tropics: Macroevolutionary size trends in an old insect order are shaped by temperature and predators

AbstractAimGlobal interspecific body size distributions have been suggested to be shaped by selection pressures arising from biotic and abiotic factors such as temperature, predation and parasitism. Here, we investigated the ecological and evolutionary drivers of global latitudinal size gradients in an old insect order.LocationGlobal.TaxonOdonata (dragonflies and damselflies).MethodsWe compiled data on interspecific variation in extant and extinct body sizes of Odonata, using an already existing database (The Odonate Phenotypic Database) and fossil data (The Paleobiology Database). We combined such body size data with latitudinal information and data on biotic and abiotic environmental variables across the globe to investigate and quantify interspecific latitudinal size‐gradients (“Bergmann's Rule”) and their environmental determinants. We used phylogenetic comparative methods and a global published phylogeny of Odonata to address these questions.ResultsPhylogenetic comparative analyses revealed that global size variation of extant Odonata taxa is negatively influenced by both regional avian diversity and temperature, with larger‐bodied species in the suborder Anisoptera (dragonflies) showing a steeper size‐latitude relationship than smaller‐bodied species in the suborder Zygoptera (damselflies). Interestingly, fossil data show that the relationship between wing size and latitude has shifted: latitudinal size trends had initially negative slopes but became shallower or positive following the evolutionary emergence and radiation of birds.Main ConclusionsThe changing size‐latitude trends over geological and macroevolutionary time were likely driven by a combination of predation from birds and maybe pterosaurs and high dispersal ability of large dragonflies. Our study reveals that a simple version of Bergmann's Rule based on temperature alone is not sufficient to explain interspecific size‐latitude trends in Odonata. Our results instead suggest that latitudinal size gradients were shaped not only by temperature but also by avian predators, potentially driving the dispersal of large‐sized clades out of the tropics and into the temperate zone.

Genetic Diversity of Paryphthimoides poltys (Nymphalidae: Satyrinae: Euptychiina) in a Fragmented Agricultural Landscape in the Brazilian Atlantic Forest

The species-level response of organisms to habitat loss and fragmentation relies on their dispersal ability, as well as trophic level, degree of habitat specialization and landscape structure. For butterflies, community composition is affected by the landscape configuration, by the surrounding habitat and by the matrix composition scattered around forest fragments, whereas higher dispersal ability is a significant advantage for persistence in highly fragmented landscapes. However, species of butterflies are highly variable in their dispersion capabilities, which affects their genetic variability as a whole and in how it is distributed within and between subpopulations in remaining fragments. In the present study, the genetic variability in subpopulations of Paryphthimoides poltys distributed through forest fragments was evaluated. Low diversity and the absence of genetic structure was found through eight fragments of semideciduous Atlantic Forest, surrounded by agricultural matrices, in Southeastern Brazil. Although P. poltys was the most common species found in the area in a previous study, its high abundance was not accompanied by high genetic variability. The species is usually found flying in forest edges and open environments and, although low, its genetic variability is expected to be preserved even if some of the investigated forest fragments are lost in the near future.

Phylogeography of a riparian earthworm shows environmental factors influence genetic structure

AbstractAimThe study of cosmopolitan earthworms could be even more interesting than that of endemic species in revealing evolutionary processes. Previous research on the cosmopolitan wormEiseniella tetraedrahas indicated some phylogeographic structure among populations, but the factors responsible remain unresolved. We hypothesized that environmental factors and dispersal have shaped the distribution of the species' lineages.LocationSpain and Portugal; Iberian Peninsula.TaxonEiseniella tetraedra(Lumbricidae, Oligochaeta, Annelida).MethodsWe collected 739 specimens ofEiseniella tetraedrafrom 65 localities around the Iberian Peninsula between 2012 and 2016. We performed phylogenetic analysis (Bayesian Inference and maximum likelihood) using two mitochondrial (COI and 16S) and one nuclear marker (28S). Furthermore, we studied their genetic diversity and historic demography based on the COI gene. Correlations between genetic diversity and 22 environmental factors were tested.ResultsEiseniella tetraedrashowed high diversity in the Iberian Peninsula, with eight different lineages nested in two clades. We found lineages mostly restricted to the northern region, while others were distributed throughout the Iberian Peninsula. Habitat stability, that is, constant availability or lack of water, also correlated with genetic diversity. Thus, although no clear phylogeographic pattern was found, environmental factors (such as precipitation, temperature, and soil pH) and habitat stability influenced the distribution of genetic variability.Main ConclusionsEiseniella tetraedrais an earthworm with great genetic variability. We show that the ranges of species with high relative dispersal ability and ambiguous phylogeographic patterns may be better explained by influence of environmental conditions rather than specific geographic features. Adaptation to unstable conditions has been shown to confer more success on one of the two major genetic clades recovered, pointing to ecological plasticity as a key for evolutionary success.

Management is more important than urban landscape parameters in shaping orthopteran assemblages across green infrastructure in a metropole

Urbanisation significantly shapes species abundance, diversity, and community structure of invertebrate taxa but the impact on orthoptera remains widely understudied. We investigated the combined effects of spatial, urban landscape and management-related parameters. Additionally, we discussed different sampling strategies. We sampled orthopteran assemblages on green infrastructure associated with the public transport system of Vienna, Austria. Sampled areas include railroad embankments, recreational areas or fallows. Using LMs, (G)LMMs and nMDS, we compared quantitative sampling using transect counts and semi-quantitative sampling which also included observations made off-transects. We found that vegetation type was the most important parameter, whereby structure-rich fallows featured highest species diversities and, together with extensive meadows, highest abundances, while intensive lawns were less suitable habitats. The semi-quantitative data set revealed an underlying species-area-relationship (SAR). Other important but highly entangled parameters were the mowing intensity, vegetational heterogeneity and cover of built-up area in a 250 m radius. Most found species have high dispersal abilities. Urban assemblages are most significantly shaped by management-related parameters on the site itself, which highlights the potential of conservation efforts in urban areas through suitable management. Sites of different vegetation types differ greatly and need adjusted management measures. Urban landscape parameters, such as the degree of soil sealing, appeared less important, likely due to the high dispersal abilities of most observed orthoptera species. The indicated species-area-relationship could be used to prioritize sites for conservation measures.

Historical biogeography and diversification of ringless Amanita (section Vaginatae) support an African origin and suggest niche conservatism in the Americas

Ectomycorrhizal fungi (ECM) sustain nutrient recycling in most terrestrial ecosystems, yet we know little about what major biogeographical events gave rise to present-day diversity and distribution patterns. Given the strict relationship between some ECM lineages and their hosts, geographically well-sampled phylogenies are central to understanding major evolutionary processes of fungal biodiversity patterns. Here, we focus on Amanita sect. Vaginatae to address global diversity and distribution patterns. Ancestral-state-reconstruction based on a 4-gene timetree with over 200 species supports an African origin between the late Paleocene and the early Eocene (ca. 56 Ma). Major biogeographic “out-of-Africa” events include multiple dispersal events to Southeast Asia (ca. 45–21 Ma), Madagascar (ca. 18 Ma), and the current Amazonian basin (ca. 45–36 Ma), the last two likely trans-oceanic. Later events originating in Southeast Asia involve Nearctic dispersal to North America (ca. 20–5 Ma), Oceania (Australia and New Zealand; ca. 15 Ma), and Europe (ca. 10–5 Ma). Subsequent dispersals were also inferred from Southeast Asia to East Asia (ca. 4 Ma); from North America to East Asia (ca. 11–8 Ma), Southeast Asia (ca. 19–2 Ma), Northern Andes (ca. 15 Ma), and Europe (ca. 15–2 Ma), respectively; and from the Amazon to the Caribbean region (ca. 25–20 Ma). Finally, we detected a significant increase in the net diversification rates in the branch leading to most northern temperate species in addition to higher state-dependent diversification rates in temperate lineages, consistent with previous findings. These results suggest that species of sect. Vaginatae likely have higher dispersal ability and higher adaptability to new environments, in particular compared to those of its sister clade, sect. Caesareae. Overall, the much wider distribution of A. sect. Vaginatae, from pan-tropical to pan-arctic, provides a unique window to understanding niche conservatism across a species-rich clade of ECM fungi.

Life-history traits drive spatial genetic structuring in Dinaric cave spiders

The subterranean ecosystem exerts strong selection pressures on the organisms that thrive in it. In response, obligate cave-dwellers have developed a series of morphological, physiological, and behavioral adaptations, such as eye reduction, appendage elongation, low metabolic rates or intermittent activity patterns, collectively referred to as troglomorphism. Traditionally, studies on cave organisms have been hampered by the difficulty of sampling (i.e., small population sizes, temporal heterogeneity in specimen occurrence, challenges imposed by the difficult-to-access nature of caves). Here, we circumvent this limitation by implementing a museomics approach. Specifically, we aim at comparing the genetic population structures of five cave spider species demonstrating contrasting life histories and levels of troglomorphism across different caves in the northern Dinarides (Balkans, Europe). We applied a genome-wide hybridization-capture approach (i.e., HyRAD) to capture DNA from 117 historical samples. By comparing the population genetic structures among five species and by studying isolation by distance, we identified deeper population structuring and more pronounced patterns of isolation by distance in the highly troglomorphic Parastalita stygia and Stalita pretneri ground dwellers, while the three web-building Troglohyphantes species, two of which can occasionally be found in surface habitats, showed less structured populations compatible with higher dispersal ability. The spatial distribution of genetic groups revealed common phylogeographic breaks among lineages across the studied species, which hint at the importance of environmental features in driving dispersal potential and shaping underground diversity.

Northeastern Asia humidification at the end of the Miocene drives the boost of mammalian dispersals from the Old to New World

Mammals have high dispersal ability, and many lineages can spread across the continents when a landbridge appears. Here, we summarize the dispersal of mammals between the Old and New World at the end of the Miocene. Our analysis suggested that the three phases of dispersal represented the largest dispersal tide during the Neogene, and the direction of dispersal is dominated by being from the Old to New World. Judging from the components that crossed the dispersal corridor, the Arctic environment near the Beringia corridor in the first phase (∼7.5 Ma) is a mixed environment, and in the second phase (∼6.5 Ma) is an open environment, and in the third phase (∼5.8 Ma and continue to the Pliocene) is a wooded (closed) environment. A clear trend of eastern Asian humidification driven by Asian monsoon and the global C4 grassland expansion explain this dispersal pattern. The boost of mammalian dispersals is controlled by the heterogeneity of environmental changes in different continents.

Examining the relative influence of dispersal and competition on co-occurrence and functional trait patterns in response to disturbance

Disturbance gradients are particularly useful for understanding the relative influences of competition and dispersal. Shortly after disturbance, plant composition should be influenced more strongly by dispersal than competition; over time, this should reverse, with competition becoming more important. As such, we predicted that plant functional traits associated with high dispersal ability would be over-represented shortly after a disturbance event occurs, while those associated with high competitive ability would have increased representation as time progresses. Additionally, it has been suggested that competitive interactions may contribute to negative co-occurrence patterns; if this is the case, negative co-occurrence patterns should also increase as time-since-disturbance increases. Here, we examine how functional trait and co-occurrence patterns change over time following a herbicide-based disturbance, compared to undisturbed vegetation, in a temperate, old-field grassland dominated by herbaceous perennials. In our study system, negative co-occurrence patterns were most pronounced in disturbed plots one year after herbicide application, consistent with several lines of evidence that dispersal can strongly impact both composition and co-occurrence patterns. Over three years post-disturbance, co-occurrence patterns in disturbed plots decreased, becoming more similar to control plots. This pattern is inconsistent with the expectation that competition contributes to negative co-occurrence patterns, at least over three growing seasons. More pronounced negative co-occurrence patterns were associated with higher species evenness among plots. Functional traits related to increased dispersal (mean seed mass, and proportion of stoloniferous/rhizomatous species) and competitive ability (mean species height, and mean specific leaf area) did not differ significantly across treatments, with the exception of mean height in the third-year post-disturbance; however, the overall trajectory of this trait was inconsistent with theoretical expectations. Overall, co-occurrence patterns changed across the gradient of time-since disturbance, but not as expected; functional trait patterns (trait means, functional diversity measures) were not responsive to our experimental disturbance gradient.

Threatened and extinct island endemic birds of the world: Distribution, threats and functional diversity

AbstractAimThe 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.LocationGlobal.TaxonBirds.MethodsWe 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 conclusionsWe 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.

Spatiotemporal influences of climate and humans on muskox range dynamics over multiple millennia.

Processes leading to range contractions and population declines of Arctic megafauna during the late Pleistocene and early Holocene are uncertain, with intense debate on the roles of human hunting, climatic change, and their synergy. Obstacles to a resolution have included an overreliance on correlative rather than process-explicit approaches for inferring drivers of distributional and demographic change. Here, we disentangle the ecological mechanisms and threats that were integral in the decline and extinction of the muskox (Ovibos moschatus) in Eurasia and in its expansion in North America using process-explicit macroecological models. The approach integrates modern and fossil occurrence records, ancient DNA, spatiotemporal reconstructions of past climatic change, species-specific population ecology, and the growth and spread of anatomically modern humans. We show that accurately reconstructing inferences of past demographic changes for muskox over the last 21,000 years require high dispersal abilities, large maximum densities, and a small Allee effect. Analyses of validated process-explicit projections indicate that climatic change was the primary driver of muskox distribution shifts and demographic changes across its previously extensive (circumpolar) range, with populations responding negatively to rapid warming events. Regional analyses show that the range collapse and extinction of the muskox in Europe (~13,000 years ago) was likely caused by humans operating in synergy with climatic warming. In Canada and Greenland, climatic change and human activities probably combined to drive recent population sizes. The impact of past climatic change on the range and extinction dynamics of muskox during the Pleistocene-Holocene transition signals a vulnerability of this species to future increased warming. By better establishing the ecological processes that shaped the distribution of the muskox through space and time, we show that process-explicit macroecological models have important applications for the future conservation and management of this iconic species in a warming Arctic.

Phylogeographic Structuring of the Kuroshio-Type Prawn Macrobrachium japonicum (Decapoda: Palaemonidae) in Taiwan and Ryukyu Islands

Oceanic currents, biological traits, and geological evidence from historical climate change have shaped the distribution of genetic diversity and demographic history in Macrobrachium japonicum. In this study, we investigated the phylogeographic structures and demographic history of M. japonicum in Taiwan and the Ryukyu Islands by the partial mitochondrial COI gene. The topology of the haplotype minimum-spanning network revealed a star-like structure, which suggested a recent range expansion. With the apparent lack of strong dispersal barriers to gene flow between ocean basins, amphidromous prawns, as marine organisms with larvae of high dispersal abilities, are generally expected to show genetic homogeneity. Divergence data suggested that M. japonicum populations diverged 0.462 ± 0.164 myr. Complex patterns of asymmetrical gene flow indicate that variation in dispersal ability is affected by the dominant Kuroshio Current systems of the Pacific Ocean. Analysis of its demographic history revealed that M. japonicum underwent a decline in size following a recent population expansion based on ABC analysis. Bayesian skyline plot analyses of all populations indicated that the expansion of M. japonicum was estimated to have occurred in 175 Kya and that the effective population size rapidly increased by approximately 50 Kya. The results of this study may offer both practical and theoretical value for the further study of conservation genetics, management, and sustainable resource utilization.