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7,883 results for “Tropic”
Image 6. A in The Odonata of Binyo Penyilam, a unique tropical wetland area in Bintulu Division, Sarawak, Malaysia
Image 6. A section of flooded forest by the Sg. Penyilam
Image 11 in The Odonata of Binyo Penyilam, a unique tropical wetland area in Bintulu Division, Sarawak, Malaysia
Image 11. Brachygonia puella female
Image 2 in The Odonata of Binyo Penyilam, a unique tropical wetland area in Bintulu Division, Sarawak, Malaysia
Image 2. Map of the sampling area.
Image 9 in The Odonata of Binyo Penyilam, a unique tropical wetland area in Bintulu Division, Sarawak, Malaysia
Image 9. Elattoneura aurantiaca male
Image 8. A in The Odonata of Binyo Penyilam, a unique tropical wetland area in Bintulu Division, Sarawak, Malaysia
Image 8. A black water pool in one of the open marshland areas
Data from: Seed-dispersal networks in tropical forest fragments: area effects, remnant species, and interaction diversity
<p>Seed dispersal interactions involve key ecological processes in tropical forests that help to maintain ecosystem functioning. Yet this functionality may be threatened by increasing habitat loss, defaunation and fragmentation. However, generalist species, and their interactions, can benefit from the habitat change caused by human disturbance while more specialized interactions mostly disappear. Therefore changes in the structure of the local, within fragment, networks can be expected. Here we investigated how the structure of seed-dispersal networks changes along a gradient of increasing habitat fragmentation. We analysed 16 bird seed-dispersal assemblages from forest fragments of a biodiversity-rich ecosystem. We found significant species-, interaction- and network-area relationships, yet the later was determined by the number of species remaining in each community. The number of frugivorous bird and plant species, their interactions, and the number of links per species decreases as area is lost in the fragmented landscape. In contrast, network nestedness has a negative relationship with fragment area, suggesting an increasing generalization of the network structure in the gradient of fragmentation. Network specialization was not significantly affected by area, indicating that some network properties may be invariant to disturbance. Still, the local extinction of partner species, paralleled by a loss of interactions and specialist-specialist bird-plant seed dispersal associations suggests the functional homogenization of the system as area is lost. Our study provides empirical evidence for network-area relationships driven by the presence/absence of remnant species and the interactions they perform.</p>
Data from: Plant community responses to stand-level nutrient fertilization in a secondary tropical dry forest
The size of the terrestrial carbon (C) sink is mediated by the availability of nutrients that limit plant growth. However, nutrient controls on primary productivity are poorly understood in the geographically extensive yet understudied tropical dry forest biome. To examine how nutrients influence above‐ and belowground biomass production in a secondary, seasonally dry tropical forest, we conducted a replicated, fully factorial nitrogen (N) and phosphorus (P) fertilization experiment at the stand scale in Guanacaste, Costa Rica. The production of leaves, wood, and fine roots was monitored through time; root colonization by mycorrhizal fungi and the abundance of N‐fixing root nodules were also quantified. In this seasonal forest, interannual variation in rainfall had the largest influence on stand‐level productivity, with lower biomass growth under drought. By contrast, aboveground productivity was generally not increased by nutrient addition, although fertilization enhanced growth of individual tree stems in a wet year. However, root growth increased markedly and consistently under P addition, significantly altering patterns of stand‐level biomass allocation to above‐ vs. belowground compartments. Although nutrients did not stimulate total biomass production at the community scale, N‐fixing legumes exhibited a twofold increase in woody growth in response to added P, accompanied by a dramatic increase in the abundance of root nodules. These data suggest that the relationship between nutrient availability and primary production in tropical dry forest is contingent on both water availability and plant functional diversity.
Data from: Early Paleocene tropical forest from the Ojo Alamo Sandstone, San Juan Basin, New Mexico, USA
Earliest Paleocene megafloras from North America are hypothesized to be low diversity and dominated by long-lived cosmopolitan species following the Cretaceous-Paleogene (K/Pg) mass extinction. However, megafloras used to develop this hypothesis are from the Northern Great Plains of North America, and relatively little is known about floras from southern basins. Here, we present a quantitative analysis of an earliest Paleocene megaflora (<350 kyr after K/Pg boundary) from the Ojo Alamo Sandstone in the San Juan Basin (SJB), New Mexico. The megaflora, comprised of 53 morphotypes, was dominated by angiosperms, with accessory taxa composed of pteridophytes, lycophytes, and conifers. Diversity analyses indicate a species rich, highly uneven, and laterally heterogeneous flora. Paleoclimate estimates using multivariate and univariate methods indicate warm temperatures and relatively high precipitation consistent with a modern tropical seasonal forest. When compared to contemporaneous floras from the Denver Basin (DB) of Colorado and the Williston Basin (WB) of North Dakota, the SJB flora had significantly higher species richness but lower evenness. Paleoclimate estimates from the SJB were 7-14 °C warmer than the DB and WB, indicating a shift from a temperate forest in the Northern Great Plains to a tropical forest in the SJB. These results demonstrate the presence of a latitudinal floral diversity and paleoclimatic gradient during the earliest Paleocene in western North America. We hypothesize that the warm, wet conditions in the earliest Paleocene SJB drove rapid rates of speciation following the K/Pg boundary resulting in a diverse and heterogenous flora.
Data from: Geo-climatic factors drive diatom community distribution in tropical South American freshwaters
1.Patterns that maintain and generate biodiversity of macro-organisms in the Neotropics are widely discussed in the scientific literature, yet the spatial ecology of microorganisms is largely unknown. The unique character of the tropical Andes and adjacent Amazon lowlands generates a wide gradient of environmental conditions to advance our understanding of what drives community assembly and diversity processes. 2.We analyzed the distribution patterns of benthic diatoms (unicellular siliceous algae) as a model group of microbial passive dispersers, including predictors that describe limnological and geo-climatic gradients for a total of 113 waterbodies (0–28ºS and 58–80ºW), including lakes and streams. Complementary multivariate statistical analyses were performed to correlate i) community composition, and ii) diatom species richness with environmental and spatial factors to infer niche-based and dispersal-based assembly processes, respectively. 3.Results showed that two gradients structured both diatom assemblages and waterbodies, namely climate and landscape configuration. Variance partitioning revealed that broad-scale spatial variables (distance-based Moran's Eigenvectors) outperformed the two environmental components (limnological and geo-climatic), suggesting dispersal-assembled communities. However, diatom assemblages were structured by geo-climatic (regional) factors in certain lakes in the northern and central Andes, although their effects were partially manifested via local variables after the geographical distances were factored out. In a similar way, climatic and topographic structuring homogenized lake and stream communities within ecoregions, as indicated by the strong overlap between the two community types and the weak correlation between biota and limnological variables. Notably, a significant increase in diatom species richness was related to increased water connectivity, interpreted to indicate that a decrease in the remoteness of the system increase species number. 4.Synthesis. We emphasize the strength of macroecological gradients (landscape configuration and climatic factors) in affecting both diatom diversity and community composition in the South American tropics. In this context, our results and the commonalities of ecoregion patterning with groups of macroorganisms (vegetation), suggest the need to integrate microbial ecology into a macroecology framework to unravel mechanisms behind diversity gradients.
Data from: Using terrestrial haematophagous leeches to enhance tropical biodiversity monitoring programmes in Bangladesh
1. Measuring mammal biodiversity in tropical rainforests is challenging, and methods which reduce effort while maximizing success are crucial for long-term monitoring programmes. Commonly used methods to assess mammal biodiversity may require substantial sampling effort to be effective. Genetic methods are a new and important sampling tool on the horizon, but obtaining sufficient DNA samples can be a challenge. 2. We evaluated the efficacy of using parasitic leeches Haemadipsa spp., as compared to camera trapping, to sample biodiversity. We collected 200 leeches from four forest patches in northeast Bangladesh, and identified recent vertebrate hosts using Sanger sequencing of the 16S rRNA gene extracted from each individual leech's blood meals. We then compared this data to species data from camera trapping conducted in the same forest patches. 3. Overall, 41.9% of sequenced leeches contained amplifiable non-human mammal DNA. Four days of collecting leeches led to the identification of 12 species, compared to 26 species identified in 1334 camera trap nights. 4. Synthesis and applications. After assessing the cost, effort, and power of each technique, there are pros and cons to both camera trapping and leech blood meal analysis. Camera trapping and leech collection appear to be complementary approaches. When used together, they may provide a more complete monitoring tool for mammal biodiversity in tropical rainforests. Managers should consider adding leech collection to their biodiversity monitoring toolkit, as improved information will allow managers to create more effective conservation programmes. R scripts are available upon request.
A catastrophic tropical drought kills hydraulically vulnerable tree species
<p>Drought-related tree mortality is now a widespread phenomenon predicted to increase in magnitude with climate change. However, the patterns of which species and trees are most vulnerable to drought, and the underlying mechanisms have remained elusive, in part due to the lack of relevant data and difficulty of predicting the location of catastrophic drought years in advance. We used long‐term demographic records and extensive databases of functional traits and distribution patterns to understand the responses of 20 to 53 species to an extreme drought in a seasonally dry tropical forest in Costa Rica, which occurred during the 2015 El Niño Southern Oscillation event. Overall, species-specific mortality rates during the drought ranged from 0% to 34%, and varied little as a function of tree size. By contrast, hydraulic safety margins correlated well with probability of mortality among species, while morphological or leaf economics spectrum traits did not. This firmly suggests hydraulic traits as targets for future research.</p>
Critical thermal maxima of early life stages of tropical fishes
<p>Marine ectotherms are often sensitive to thermal stress, and certain life stages can be particularly vulnerable (e.g., larvae or spawners). In this study, we investigated the critical thermal maxima (CT<sub>max</sub>) of larval and early juvenile life stages of three tropical marine fishes (<i>Acanthochromis polyacanthus</i>, <i>Amphiprion melanopus,</i> and <i>Lates calcarifer</i>). We tested for potential effects of developmental acclimation, life stage, and experimental heating rates, and we measured metabolic enzyme activities from aerobic (citrate synthase, CS) and anaerobic pathways (lactate dehydrogenase, LDH). A slightly elevated rearing temperature neither influenced CT<sub>max</sub> nor CS activity, which otherwise could have indicated thermal acclimation. However, we found species- and life stage-specific differences in CT<sub>max</sub> that were mainly explained by body mass, with faster heating rates leading to higher CT<sub>max</sub>. Acute temperature stress did not change CS or LDH activities, suggesting that overall aerobic and anaerobic metabolism remained stable. <i>Lates calcarifer</i>, a catadromic species that migrates from oceanic to riverine habitats upon metamorphosis, had higher CT<sub>max</sub> than the two coral reef fish species. We highlight that, for obtaining conservative estimates of a fish species' upper thermal limit, several developmental stages and body mass ranges should be examined. Moreover, upper thermal limits should be assessed using standardized heating rates. This will not only benefit comparative approaches but also aid in assessing geographic (re-) distributions and climate change sensitivity of marine fishes.</p>
Data from: Female ornamentation is associated with elevated aggression and testosterone in a tropical songbird
In males, testosterone plays a key role in ornament production and linking ornamentation with reproductive behaviors and other traits to produce an integrated phenotype. Less is known about whether females couple testosterone, ornamentation, and aggressive behaviors to achieve female-specific combinations of traits. Ornamentation in females may be the result of correlated expression with male ornamentation, or female traits could arise as the result of sex specific selection pressures. Resolving between these alternatives is necessary to understand the degree to which selection acts on female traits. The White-shouldered Fairywren (Malurus alboscapulatus) provides a useful context to address these questions because populations vary in degree of female ornamentation, a derived trait, whereas male ornamentation is constant across both populations. We found that ornamented females have higher levels of circulating testosterone and respond more aggressively to experimental territorial intrusions than do unornamented females. These findings are consistent with the idea that, among female White-shouldered Fairywrens, testosterone may mechanistically link plumage and behavioral traits to produce an integrated competitive phenotype, as has been reported for males of closely related species. In contrast, circulating testosterone in males did not differ significantly between populations. More broadly, our findings are consistent with ongoing selection on the mechanisms underlying female ornaments, likely via social selection.
Data from: Tropical bird species have less variable body sizes
Ecologists have often predicted that species' niche breadths should decline toward the equator. Dan Janzen arrived at this prediction based on climatic constraints, while Robert MacArthur argued that a latitudinal gradient in resource specialization drives the pattern. This idea has some support when it comes to thermal niches, but has rarely been explored for other niche dimensions. Body size is linked to niche dimensions related to diet, competition, and environmental tolerance in vertebrates. We identified 68 pairs of tropical and nontropical sister bird species using a comprehensive phylogeny and used the VertNet specimen database to ask whether tropical birds have lower intraspecific body-size variation than their nontropical sister species. Our results show that tropical species have less intraspecific variability in body mass ( = 0.0092; p = 0.009). Variation in body-size variability was poorly explained by both abiotic and biotic drivers, thus the mechanisms underlying the pattern are still unclear. The lower variation in body size of tropical bird species may have evolved in response to more stable climates and resource environments.
Data from: Cenozoic colonization and diversification patterns of tropical American palms: evidence from Astrocaryum (Arecaceae)
With 788 species in 67 genera in the Neotropics, Arecaceae are an important ecological and economic component of the region. We review the influence of geological events such as the Pebas system, the Andean uplift and the land connections between South and Central/North America, on the historical assembly of Neotropical palms. We present a case study of the palm genus Astrocaryum (40 species) as a model for evaluating colonization and diversification patterns of lowland Neotropical taxa. We conducted a Bayesian dated phylogenetic analysis based on four low-copy nuclear DNA regions and a biogeographical analysis using the dispersal, extinction and cladogenesis model. Cladogenesis of Western Amazonian Astrocaryum spp. (c. 6 Mya) post-dated the drainage of the aquatic Pebas system, supporting the constraining role of Pebas on in situ diversification and colonization. The ancestral distribution of Astrocaryum spp. in the Guiana Shield supported the hypothesis of an old formation that acted as a source area from which species colonized adjacent regions, but an earliest branching position for Guianan species was not confidently recovered. A twofold increase in diversification rate was found in a clade, the ancestor of which occupied the Guiana Shield (c. 13 Mya, a time of climatic change and Andean uplift).
Data from: Leaf drought tolerance cannot be inferred from classic leaf traits in a tropical rainforest
<ol> <li>Plants are enormously diverse in their traits and ecological adaptation, even within given ecosystems, such as tropical rainforests. Accounting for this diversity in vegetation models poses serious challenges. Global plant functional trait databases have highlighted general trait correlations across species that have considerably advanced this research program. However, it remains unclear whether trait correlations found globally hold within communities, and whether they extend to drought tolerance traits.</li> <li>For 134 individual plants spanning a range of sizes and life forms (tree, liana, understory species) within an Amazonian forest, we measured leaf drought tolerance (leaf water potential at turgor loss point, π<sub>tlp</sub>), together with 17 leaf traits related to various functions, including leaf economics traits and nutrient composition (leaf mass per area, LMA; and concentrations of C, N, P, K, Ca, and Mg per leaf mass and area), leaf area, water use efficiency (carbon isotope ratio), and time-integrated stomatal conductance and carbon assimilation rate per leaf mass and area. We tested trait coordination and the ability to estimate π<sub>tlp</sub> from the other traits through model selection. Performance and transferability of the best predictive model were assessed through cross-validation.</li> <li>π<sub>tlp</sub> was positively correlated with leaf area, and with N, P and K concentrations per leaf mass, but not with LMA or any other studied trait. Five axes were needed to account for >80% of trait variation, but only three of them explained more variance than expected at random. The best model explained only 30% of the variation in π<sub>tlp</sub>, and out-sample predictive performance was variable across life forms or canopy strata, suggesting a limited transferability of the model.</li> <li> <i>Synthesis</i>. We found a weak correlation among leaf drought tolerance and other leaf traits within a forest community. We conclude that higher trait dimensionality than assumed under the leaf economics spectrum may operate among leaves within plant communities, with important implications for species coexistence and responses to changing environmental conditions, and also for the representation of community diversity in vegetation models.</li> </ol>
Data from: Gene duplication, population genomics and species-level differentiation within a tropical mountain shrub
Gene duplication leads to paralogy, which complicates the de novo assembly of genotyping-by-sequencing (GBS) data. The issue of paralogous genes is exacerbated in plants, because they are particularly prone to gene duplication events. Paralogs are normally filtered from GBS data before undertaking population genomics or phylogenetic analyses. However, gene duplication plays an important role in the functional diversification of genes and it can also lead to the formation of postzygotic barriers. Using populations and closely related species of a tropical mountain shrub, we examine: (1) the genomic differentiation produced by putative orthologs, and (2) the distribution of recent gene duplication among lineages and geography. We find high differentiation among populations from isolated mountain peaks and species-level differentiation within what is morphologically described as a single species. The inferred distribution of paralogs among populations is congruent with taxonomy and shows that GBS could be used to examine recent gene duplication as a source of genomic differentiation of non-model species.
Data from: Do lianas shape ant communities in an early successional tropical forest?
Almost half of lowland tropical forests are at various stages of regeneration following deforestation or fragmentation. Changes in tree communities along successional gradients have predictable bottom-up effects on consumers. Liana (woody vine) assemblages also change with succession, but their effects on animal succession remain unexplored. Here we used a large-scale liana removal experiment across a forest successional chronosequence (7-31 years) to determine the importance of lianas to ant community structure. We conducted 1088 surveys of ants foraging on and living in trees using tree trunk baiting and hand collecting techniques at 34 paired forest plots, half of which had all lianas removed. Ant species composition, β-diversity, and species richness were not affected by liana removal; however, ant species co-occurrence (the coexistence of two or more species in a single tree) was more frequent in control plots, where lianas were present, vs. removal plots. Forest stand age had a larger effect on ant community structure than the presence of lianas. Mean ant species richness in a forest plot increased by ca. 10% with increasing forest age across the 31-year chronosequence. Ant surveys from forest >20 years old included more canopy specialists and fewer ground-nesting ant species vs. those from forests <20 years old. Consequently, lianas had a minimal effect on arboreal ant communities in this early-successional forest, where rapidly changing tree community structure was more important to ant species richness and composition.
Data from: A test of community assembly rules using foliar endophytes from a tropical forest canopy
<p>Community assembly theory assumes that ecological communities are spatially delimited into patches. Within these patches, coexistence results from environmental filtering, competition, and immigration. Truly delineated communities exist in laboratory studies of microbial cultures in Petri dishes, yet empirical tests conducted in continuous environments often use patches defined by convention as opposed to realised boundaries. Here we perform a test of ecological community assembly rules using foliar endophyte communities from a tropical rainforest, where leaves are considered as patches for both fungal and bacterial communities. We determined the diversity of fungal and bacterial endophytes using environmental DNA sequencing of 365 top-canopy leaves, collected from 38 host trees belonging to 22 different species across a 4-hectare research plot. Three leaves were collected from three or more branches within each tree crown. We tested the effect of host tree species and their level of phylogenetic relatedness on community composition as well as the contribution of geographic distance between leaves to endophyte community diversity. Endophyte diversity significantly differed across host tree species, as did community composition. Within certain endophytic orders (Xylariales, Rhizobiales) species assemblages significantly differed across host tree species, but this trend was weaker or non-existent in other orders known to contain pathogens and saprotrophs (Polyporales, Solirubrobacterales). Phylogenetically related host tree species displayed more similar endophyte communities than expected by chance, but geographically close trees did not. Consistent with the finding of host-specificity, nearby leaves tended to host more similar communities than distantly positioned ones. These findings demonstrate that foliar endophytes are structured by dispersal across small spatial scales, but at the scale of the canopy they display patterns of neutral filtering, with only a small part of variation described by host tree differences. Endophyte communities thus act as a model system in evoking the rules predicted by theoretical community ecology.</p>
Data from: Effects of soil type and light on height growth, biomass partitioning, and nitrogen dynamics on 22 species of tropical dry forest tree seedlings: comparisons between legumes and nonlegumes
PREMISE OF THE STUDY: The seedling stage is particularly vulnerable to resource limitation, with potential consequences for community composition. We investigated how light and soil variation affected early growth, biomass partitioning, morphology, and physiology of 22 tree species common in tropical dry forest, including eight legumes. Our hypothesis was that legume seedlings are better at taking advantage of increased resource availability, which contributes to their successful regeneration in tropical dry forests. METHODS: We grew seedlings in a full-factorial design under two light levels in two soil types that differed in nutrient concentrations and soil moisture. We measured height biweekly and, at final harvest, biomass partitioning, internode segments, leaf carbon, nitrogen, δ 13 C, and δ 15 N. KEY RESULTS: Legumes initially grew taller and maintained that height advantage over time under all experimental conditions. Legumes also had the highest final total biomass and water-use efficiency in the high-light and high-resource soil. For nitrogen-fixing legumes, the amount of nitrogen derived from fixation was highest in the richer soil. Although seed mass tended to be larger in legumes, seed size alone did not account for all the differences between legumes and nonlegumes. Both belowground and aboveground resources were limiting to early seedling growth and function. CONCLUSIONS: Legumes may have a different regeneration niche, in that they germinate rapidly and grow taller than other species immediately after germination, maximizing their performance when light and belowground resources are readily available, and potentially permitting them to take advantage of high light, nutrient, and water availability at the beginning of the wet season.
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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.