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140 results for “tropical islands”
Data from: Application of a trait‐based species screening framework for vegetation restoration in a tropical coral island of China
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Radiation of tropical island bees and the role of phylogenetic niche conservatism as an important driver of biodiversity
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Species Abundance Distributions (SADs) for local tree communities in 1-ha forest plots on 20 tropical islands in the Indo-Pacific region
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Data from: Long-term in situ persistence of biodiversity in tropical sky-islands revealed by landscape genomics
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Insect seed-predator networks respond positively to restoration on a tropical island
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Environmental DNA metabarcoding to monitor tropical reef fishes in Providencia island
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Chronic browsing by an introduced mammalian herbivore in a tropical island alters species composition and functional traits of forest understory plant communities
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FIGURE 9 in First record of Synagelides Strand, 1906 (Araneae: Salticidae) from Sri Lanka description of four endemic species from tropical wet forest of the island
FIGURE 9. Synagelides orlandoi sp. nov. A–B, male (A, dorsal view; B, ventral view). C–E left palp (C, prolateral view; D, ventral view; E, retrolateral view). Scale bars: A–B = 0.5 mm, C–E = 0.1 mm.
Allopatric instead of parapatric divergence in an ectomycorrhizal fungus (Laccaria trichodermophora) in tropical sky-islands
<p>In tropical sky-islands, cold-affinity populations tend to become isolated at highlands during the interglacial periods, and to expand into the lowlands where they become more connected during the glacial periods. Although this has been widely studied in trees, it is poorly understood how fungal symbionts can differentiate among mountains (allopatrically), or within a single mountain (parapatrically) due to climate fluctuations. Here, we conducted population genomic analyses on the ectomycorrhizal fungus Laccaria trichodermophora in three tropical sky-islands using Genotyping by Sequencing (GBS) at low DNA concentrations. There were no significant differences between altitudes within a single mountain, but we observed significant genetic differentiation among populations from different mountains, supporting the allopatric differentiation hypothesis. Our results indicate that L. trichodermophora populations are under a sky-island population dynamics that started during the Pleistocene climate fluctuations.</p>
Structure of small tropical islands freshwater fish and crustacean communities: a niche- or dispersal-based process?
Determining the relative importance of niche- and dispersal-based processes in the structuring of animal communities is central in ecology. Freshwater fish and crustacean communities of small tropical islands can bring new insights for understanding these processes as all their species present a pelagic larval stage which gives them important dispersal capacities. Consequently, we hypothesized that dispersal-based process maybe preponderant for structuring these communities from the regional- to the local, i.e. survey site, scales. Gradient forest analyses allowed us to model the effect of 12 environmental variables on freshwater taxa abundances in two southwestern Indian Ocean islands: Mayotte (26 taxa) and Reunion (21). A total of 153 surveys in Mayotte and 266 in Reunion were used for building the models. Despite the strong heterogeneity of environmental conditions between the two islands, the main factors structuring freshwater fish and crustacean communities in both islands were the elevation and the slope of the sites. The observed structure appeared more pronounced for predatory species than for primary consumers and omnivores. As predators generally have limited locomotor capacities, it is concluded that dispersal-based process structures these communities not only at large geographical scales but also at the intra-watershed scale, by limiting the inland penetration (or dispersion) of species in relation to their locomotor capacities. However, more knowledge concerning ecological traits and taxonomic status of many species is needed to confirm this assumption.
RAD-seq reveals patterns of diversification, hybridization, and the accumulation of reproductive isolation in a clade of partially sympatric, tropical island trees
<p>A common pattern observed in temperate tree clades is that species are often morphologically distinct and partially interfertile but maintain species cohesion despite ongoing hybridization where ranges overlap. Although closely related species commonly occur in sympatry in tropical ecosystems, little is known about patterns of hybridization within a clade over time, and the implications of this hybridization for the maintenance of species boundaries. In this study, we focused on a clade of sympatric trees in the genus <i>Diospyros</i> in the Mascarene islands and investigated whether species are genetically distinct, whether they hybridize, and how patterns of hybridization are related to the time since divergence among species. We sampled multiple populations from each of 12 Mascarene <i>Diospyros</i> species, generated genome-wide SNP data using 2bRADseq, and conducted population genomic and phylogenomic analyses. We found that Mascarene <i>Diospyros</i> species diverged millions of years ago and are largely genetically distinct from one another. Although hybridization was observed between closely related species belonging to the same subclade, more distantly related species showed little evidence of interspecific hybridization. Phylogenomic analyses also suggested that introgression occurred during the evolutionary history of the clade. This suggests that, as diversification progressed, interspecific hybridization also occurred among species, but became infrequent as lineages diverged from one another and evolved reproductive barriers. Species now co-exist in partial sympatry, and experience limited hybridization between close relatives. Additional research is needed to better understand the role introgression may have played in adaptation and diversification of Mascarene <i>Diospyros,</i> and its relevance for conservation.</p>
Data from: Life-history dimensions indicate non-random assembly processes in tropical island tree communities
<p>Community assembly processes on islands are often non-random. The mechanisms behind non-random assembly, however, are generally difficult to disentangle. Functional diversity in combination with a null model approach that accounts for differences in species richness among islands can be used to test for non-random assembly processes, but has been applied rarely to island communities. By linking functional diversity of trees on islands with a null model approach, we bridge this gap and test for the role of stochastic vs. non-random trait-mediated assembly processes in shaping communities by studying functional diversity-area relationships. We measured 11 plant functional traits linked to species dispersal and resource acquisition strategies of 57 tree species on 40 tropical islands. We grouped traits into four life-history dimensions representing (i) dispersal ability, (ii) growth strategy, (iii) light acquisition, and (iv) nutrient acquisition. To test for non-random assembly processes, we used null models that account for differences in species richness among the islands. Our results reveal contrasting responses of the four life-history dimensions to island area. The dispersal and the growth strategy dimensions were underdispersed on smaller islands, whereas the light acquisition dimension was overdispersed. The nutrient acquisition dimension did not deviate from null expectations. With increasing island area, shifts in the strength of non-random assembly processes increased the diversity of dispersal and acquisition strategies in island communities. Our results suggest that smaller islands may be more difficult to colonize and provide more limited niche space compared to larger islands, whose tree communities are likely determined by stochastic processes and higher niche diversity. Our null model approach highlights that analysing the functional diversity of different life-history dimensions provides a powerful framework to unravel community assembly processes on islands. These complex, non-random assembly processes are masked by measures of functional diversity that do not account for differences in species richness between islands.</p>
Data from: Tropical trees in a wind-exposed island ecosystem: height-diameter allometry and size at onset of maturity
1. Tropical tree species adapted to high wind environments might be expected to differ systematically in terms of stem allometry and life-history patterns, as compared with species found in less windy forests. We quantified height-diameter (H-D) allometries and relative size at onset of maturity (RSOM) for rainforest tree and tree fern species native to Dominica, West Indies, an island that experiences some of the highest average wind speeds pantropically. 2. H-D allometries for 17 Dominican angiosperm tree species were strongly concave on a log-log scale with asymptotic heights ranging from 9-32 m among species, averaging 25 m for canopy trees. H-D allometries for species-pooled data deviated strongly from recorded patterns for other tropical forest trees: asymptotic heights for trees in Dominica were 30-116% lower than those recorded for continental rainforest trees in Australia, South America, Africa, and Southeast Asia. In a subset of canopy trees sampled in steep, sheltered valleys, heights were 12-26% larger at a given diameter, and approached those observed in other tropical regions, suggesting large phenotypic responses of H-D allometries to wind conditions. 3. RSOM (quantified as the ratio of height at onset of reproduction to asymptotic maximum height) for Dominican angiosperm species was highly variable, ranging from 0.23-0.89 (mean 0.54), similar to patterns observed in Malaysia and Panama; very low RSOM values were estimated for two tree fern species. Pooling data from Dominica with published values from other tropical forests, we observed a significant negative correlation between RSOM and wood density. 4. Synthesis: Our data suggest that wind regimes are a critical determinant of height-diameter (H-D) allometries of tropical trees at both the local and global scale. Although we found no evidence for a systematic differences in reproductive onset related to wind regime, RSOM was negatively correlated with species' wood density, suggesting that more shade-tolerant tree species show a longer period of gradually increasing reproductive allocation through ontogeny.
Data from: Pleistocene speciation with and without gene flow in Euphaea damselflies of subtropical and tropical East Asian islands
Climatic oscillations during the Pleistocene period could have had a profound impact on the origin of tropical species by the alternation of allopatric isolation and inter-population gene flow cycles. However, whether tropical speciation involves strictly allopatric isolation, or proceeds in the face of homogenizing gene flow, is relatively unclear. Here, we investigated geographical modes of speciation in four closely-related Euphaea damselfly species endemic to the subtropical and tropical East Asian islands using coalescent analyses of a multi-locus data set. The reconstructed phylogenies demonstrated distinct species status for each of the four species and the existence of two sister species pairs, E. formosa/E. yayeyamana and E. decorata/E. ornata. The species divergence time of the sibling Euphaea damselflies dates back to within the last one Mya of the Middle to Lower Pleistocene. The speciation between the populous E. formosa of Taiwan and the less numerous E. yayeyamana of the Yaeyama islands occurred despite significant bidirectional, asymmetric gene flow, which is strongly inconsistent with a strictly allopatric model. In contrast, speciation of the approximately equal-sized populations of E. decorata of the south-east Asian mainland and E. ornata of Hainan is inferred to have involved allopatric divergence without gene flow. Our findings suggest that differential selection of natural or sexual environments is a prominent driver of species divergence in subtropical E. formosa and E. yayeyamana; whereas for tropical E. decorata and E. ornata at lower latitudes, allopatric isolation may well be a pivotal promoter of species formation.
Data from: Not seeing the grass for the trees: timber plantations and agriculture shrink tropical montane grassland by two-thirds over four decades in the Palani Hills, a Western Ghats Sky Island
Tropical montane habitats, grasslands, in particular, merit urgent conservation attention owing to the disproportionate levels of endemic biodiversity they harbour, the ecosystem services they provide, and the fact that they are among the most threatened habitats globally. The Shola Sky Islands in the Western Ghats host a matrix of native forest-grassland matrix that has been planted over the last century, with exotic timber plantations. The popular discourse on the landscape change is that mainly forests have been lost to the timber plantations and recent court directives are to restore Shola forest trees. In this study, we examine spatiotemporal patterns of landscape change over the last 40 years in the Palani Hills, a significant part of the montane habitat in the Western Ghats. Using satellite imagery and field surveys, we find that 66% of native grasslands and 31% of native forests have been lost over the last 40 years. Grasslands have gone from being the dominant, most contiguous land cover to one of the rarest and most fragmented. They have been replaced by timber plantations and, to a lesser extent, expanding agriculture. We find that the spatial pattern of grassland loss to plantations differs from the loss to agriculture, likely driven by the invasion of plantation species into grasslands. We identify remnant grasslands that should be prioritised for conservation and make specific recommendations for conservation and restoration of grasslands in light of current management policy in the Palani Hills, which favours large-scale removal of plantations and emphasises the restoration of native forests.
Data from: One species for one island? Unexpected diversity and weak connectivity in a widely distributed tropical hydrozoan
Isolation by distance (IBD) is one of the main modes of differentiation in marine species, above all in species presenting low dispersal capacities. This study reports the genetic structuring in the tropical hydrozoan Lytocarpia brevirostris α (sensu Postaire et al, 2016b), a brooding species, from 13 populations in the Western Indian Ocean (WIO) and one from New Caledonia (Tropical Southwestern Pacific). At the local scale, populations rely on asexual propagation at short distance, which was not found at larger scales; identical genotypes were restricted to single populations. After the removal of repeated genotypes, all populations presented significant positive FIS values (between 0.094*** and 0.335***). Gene flow was extremely low at all spatial scales, between sites within islands (<10 km distance) and among islands (100 to>11 000 km distance), with significant pairwise FST values (between 0.012*** and 0.560***). A general pattern of IBD was found at the Indo-Pacific scale, but also within sampled ecoregions of the WIO province. Clustering analyses identified each sampled island as an independent population, whereas analysis of molecular variance indicated that population genetic differentiation was significant at small (within island) and intermediate (among islands within province) spatial scales. The high population differentiation might reflect the life cycle of this brooding hydrozoan, possibly preventing regular dispersal at distances more than a few kilometres and probably leading to high cryptic diversity, each island housing an independent evolutionary lineage.
Data from: Linking vital rates of landbirds on a tropical island to rainfall and vegetation greenness
Remote tropical oceanic islands are of high conservation priority, and they are exemplified by range-restricted species with small global populations. Spatial and temporal patterns in rainfall and plant productivity may be important in driving dynamics of these species. Yet, little is known about environmental influences on population dynamics for most islands and species. Here we leveraged avian capture-recapture, rainfall, and remote-sensed habitat data (enhanced vegetation index [EVI]) to assess relationships between rainfall, vegetation greenness, and demographic rates (productivity, adult apparent survival) of three native bird species on Saipan, Northern Mariana Islands: rufous fantail (Rhipidura rufifrons), bridled white-eye (Zosterops conspicillatus), and golden white-eye (Cleptornis marchei). Rainfall was positively related to vegetation greenness at all but the highest rainfall levels. Temporal variation in greenness affected the productivity of each bird species in unique ways. Predicted productivity of rufous fantail was highest when dry and wet season greenness values were high relative to site-specific 5-year seasonal mean values (i.e., relative greenness); while the white-eye species had highest predicted productivity when relative greenness contrasted between wet and dry seasons. Survival of rufous fantail and bridled white eye was positively related to relative dry-season greenness and negatively related to relative wet-season greenness. Bridled white-eye survival also showed evidence of a positive response to overall greenness. Our results highlight the potentially important role of rainfall regimes in affecting population dynamics of species on oceanic tropical islands. Understanding linkages between rainfall, vegetation, and animal population dynamics will be critical for developing effective conservation strategies in this and other regions where the seasonal timing, extent, and variability of rainfall is expected to change in the coming decades.
FIGURE 18 in Alpheid shrimps (Decapoda: Caridea) of the Trindade & Martin Vaz Archipelago, off Brazil, with new records, description of a new species of Synalpheus and remarks on zoogeographical patterns in the oceanic islands of the tropical southern Atlantic
FIGURE 18. Zoogeographical components of the alpheid fauna of the oceanic islands in the tropical southern Atlantic, indicated by percentages: ADR, Atol das Rocas; ASC, Ascension Island; CVA, Cape Verde Archipelago; FDN, Fernando de Noronha Archipelago; GOG, Gulf of Guinea: São Tomé, Príncipe and Annobón Islands; SPP, São Pedro & São Paulo Archipelago; STH, Saint Helena Island. TMV, Trindade & Martin Vaz Archipelago. Other abbreviations: AA, amphi-Atlantic component; EA, eastern Atlantic component; En, endemic component; WA, western Atlantic component.
FIGURE 17 in Alpheid shrimps (Decapoda: Caridea) of the Trindade & Martin Vaz Archipelago, off Brazil, with new records, description of a new species of Synalpheus and remarks on zoogeographical patterns in the oceanic islands of the tropical southern Atlantic
FIGURE 17. Patterns of the alpheid species richness in the tropical southern Atlantic Ocean. Circle diameters are sized in proportion to the number of species in each area. Numbers inside brackets refer to alpheid species richness: ADR (25), Atol das Rocas; ASC (14), Ascension Island; CBR (69), continental coast and shelf of Brazil from Amapá to Rio Grande do Sul (including Abrolhos Archipelago); CUA (4), continental coast and shelf of Uruguay and Argentina (including Falkland/ Malvinas Islands); CVA (22), Cape Verde Archipelago; FDN (23), Fernando de Noronha Archipelago; FMC (41), North Carolina to Florida and Texas, Gulf of Mexico, Caribbean Sea, Bahamas, and Bermuda (indicating total number of species shared with South Atlantic); GOG (30), Gulf of Guinea: São Tomé, Príncipe and Annobón Islands; NCS (10), North Chain Seamounts; SPP (1), São Pedro & São Paulo Archipelago; STH (6), Saint Helena Island; TMV (21), Trindade & Martin Vaz Archipelago; VTS (6), Vitória-Trindade Seamounts Chain; WAC (27), West African continental coast and shelf from Senegal to Namibia. Abbreviations for oceanic currents: AEU, Atlantic Equatorial Undercurrent; BC, Brazil Current; CC, Canary Current; GC, Guinea Current; NEC, North Equatorial Current; NECC, North Equatorial Countercurrent; SEC, South Equatorial Current; SECC, South Equatorial Countercurrent. Circles with the same colour and diameter indicate similar species richness.
FIGURE 15 in Alpheid shrimps (Decapoda: Caridea) of the Trindade & Martin Vaz Archipelago, off Brazil, with new records, description of a new species of Synalpheus and remarks on zoogeographical patterns in the oceanic islands of the tropical southern Atlantic
FIGURE 15. Synalpheus trinitatis sp. nov., paratype, male from Trindade Island, Enseada dos Portugueses (MZUSP 33316): A—right (major) chela, lateral view; B—same, detail of distodorsal protuberance; C—left uropod, dorsal view.
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.