Niche Position Research Articles

Phylogenetic conservatism of climatic niche in bats

AbstractAimBats are commonly considered in the literature as an example of strong niche conservatism. However, no specific tests have been conducted to investigate the extent to which bat species niches are evolutionarily conserved. We address this question at different phylogenetic scales using phylogenetic and geographical approaches.LocationGlobal.MethodsWe used nine climatic variables to describe a multivariate representation of bat climatic niches. We measured niche position, niche breadth and niche overlap between sister species pairs. We performed a Mantel test to verify whether niche overlap was related to phylogenetic distance among species. We also tested for phylogenetic signal and compared the relative fit of evolutionary models with the observed variation of niche features.ResultsNiche overlap and phylogenetic distances were not related. At deeper evolutionary scales, we found evidence that climatic niche evolved more slowly than expected under a Brownian motion model. This indicates phylogenetic conservatism, particularly for niche position of Vespertilionidae and Molossidae.Main conclusionsWe found evidence of phylogenetic niche conservatism at the order and family levels but not at the species level. Evolution of climatic niches is non‐stationary across the order Chiroptera, consistent with the different histories of clades. We stress the importance of taking into account the method of choice, the niche feature and the phylogenetic scale being evaluated when testing for phylogenetic niche conservatism at higher taxonomic levels and its influence on biodiversity gradients.

Seed bank, seed size and dispersal in moisture gradients of temporary pools in Southern France

Plants reduce risk of extinction due to unpredictable rainfall by soil seed banks, dispersal or large seeds. However, seed size also increases independently in dry habitats, and since seed size is in a trade-off with seed number, size of seed banks is expected to increase in moister habitats. Therefore, we wanted to test if seed abundance in soil increases in wet habitats, if seed size increases in dry habitats, and if spread of seeds along the gradient is higher for plants of intermediate habitats in local moisture gradients.We studied 15 temporary pools in three biogeographically separated wetlands in Southern France. For each pool we studied five different moisture levels, totalling 75 local plant communities. We quantified soil seed bank by the seedling emergence method, seed size and an index of spatial spread of seeds in the soil for every species. We also quantified water levels for each plot.We found increasing abundance of seeds in the soil with increasing water levels but lower seed size and higher spread at intermediate water levels. When we controlled for niche position, we found no trade-off between seed size, spread and abundance in the soil seed bank.Type and importance of risk reduction strategies thus appeared to be strongly driven by the plant species’ moisture niche and the spatial arrangement of water levels.

Microhabitat and Climatic Niche Change Explain Patterns of Diversification among Frog Families.

A major goal of ecology and evolutionary biology is to explain patterns of species richness among clades. Differences in rates of net diversification (speciation minus extinction over time) may often explain these patterns, but the factors that drive variation in diversification rates remain uncertain. Three important candidates are climatic niche position (e.g., whether clades are primarily temperate or tropical), rates of climatic niche change among species within clades, and microhabitat (e.g., aquatic, terrestrial, arboreal). The first two factors have been tested separately in several studies, but the relative importance of all three is largely unknown. Here we explore the correlates of diversification among families of frogs, which collectively represent ∼88% of amphibian species. We assemble and analyze data on phylogeny, climate, and microhabitat for thousands of species. We find that the best-fitting phylogenetic multiple regression model includes all three types of variables: microhabitat, rates of climatic niche change, and climatic niche position. This model explains 67% of the variation in diversification rates among frog families, with arboreal microhabitat explaining ∼31%, niche rates ∼25%, and climatic niche position ∼11%. Surprisingly, we show that microhabitat can have a much stronger influence on diversification than climatic niche position or rates of climatic niche change.

Neuroblast niche position is controlled by Phosphoinositide 3-kinase-dependent DE-Cadherin adhesion

Correct positioning of stem cells within their niche is essential for tissue morphogenesis and homeostasis. How stem cells acquire and maintain niche position remains largely unknown. Here, we show that a subset of brain neuroblasts (NBs) in Drosophila utilize Phosphoinositide 3-kinase (PI3-kinase) and DE-cadherin to build adhesive contact for NB niche positioning. NBs remain within their native microenvironment when levels of PI3-kinase activity and DE-cadherin are elevated in NBs. This occurs through PI3-kinase-dependent regulation of DE-Cadherin-mediated cell adhesion between NBs and neighboring cortex glia, and between NBs and their ganglion mother cell daughters. When levels of PI3-kinase activity and/or DE-Cadherin are reduced in NBs, NBs lose niche position and relocate to a non-native brain region that is rich in neurosecretory neurons, including those that secrete some of the Drosophila insulin-like peptides. Linking levels of PI3-kinase activity to the strength of adhesive attachment could provide cancer stem cells and hematopoietic stem cells with a means to cycle from trophic-poor to trophic-rich microenvironments.

Neuroblast niche position is controlled by Phosphoinositide 3-kinase-dependent DE-Cadherin adhesion.

Correct positioning of stem cells within their niche is essential for tissue morphogenesis and homeostasis. How stem cells acquire and maintain niche position remains largely unknown. Here, we show that a subset of brain neuroblasts (NBs) in Drosophila utilize Phosphoinositide 3-kinase (PI3-kinase) and DE-cadherin to build adhesive contact for NB niche positioning. NBs remain within their native microenvironment when levels of PI3-kinase activity and DE-cadherin are elevated in NBs. This occurs through PI3-kinase-dependent regulation of DE-Cadherin-mediated cell adhesion between NBs and neighboring cortex glia, and between NBs and their ganglion mother cell daughters. When levels of PI3-kinase activity and/or DE-Cadherin are reduced in NBs, NBs lose niche position and relocate to a non-native brain region that is rich in neurosecretory neurons, including those that secrete some of the Drosophila insulin-like peptides. Linking levels of PI3-kinase activity to the strength of adhesive attachment could provide cancer stem cells and hematopoietic stem cells with a means to cycle from trophic-poor to trophic-rich microenvironments.

An Assessment of Dog Behaviour with Regard to Scientific Research Findings

Dogs have been used in the field of law enforcement for over 100 years . Despite advances in the overall performance of police officers due to improved training methods and use of various innovative devices, it is hard to imagine a fully effective police force operating without the involvement of specialist dog - handler teams. T he uniformed services generally hold in high regard the role that a well - trained canine team can play, serving as an essential deterrent to criminal activity, as well as assisting police departments in the locating of illegal drugs and explosives, in track ing fugitives and with finding missing persons or locating bodies . An understanding of general dog behaviour and interaction with different environments are essential elements, not only in the case of assessing candidate suitability for different types of training programme but also for behaviour evaluation of a companion animal. The ever - increasing demand for both working and pet dogs has seen the study of dog behaviour find itself a niche position in the realm of scientific research.

Correlates of ecological-niche diversity and extinction risk of amphibians in China under climate change

In the present study, we measured spatiotemporal properties of ecological niches of amphibians in China and tested the relative importance of various niche-diversity metrics for explaining the evolutionary distinctiveness-weighted extinction risk (EDGE) of amphibian species. We applied the hierarchical partitioning technique on the phylogenetically independent contrasts of the niche covariates and EDGE of amphibians, for the purpose of removing the influence of evolutionary inertia among species. As a comparison, phylogenetic least-square general regression (PLGS) was also conducted. The results showed that EDGE was high for those amphibian species of China identified as Critically Endangered or Endangered on the IUCN Red List. Niche fragmentation dimension (NFD) and niche position (NP) were the top two predictors across partial correlation analyses, hierarchical variation partitioning, PLGS and multiple regression analyses. Most temporal niche properties were not significantly associated with the EDGE index of amphibians. Variation partitioning analysis showed that the spatial component of niche measures explained the largest proportion of total variation in EDGE (~31%), whereas the temporal component of niche properties explained ~8% of the variation. The significantly negative role of NFD and extinction risk of amphibians in China may be attributed to a reduced rescue effect, habitat geometry, and local extinction in species with large and continuous distributional ranges.

Forest vegetation in western Romania in relation to climate variables: Does community composition reflect modelled tree species distribution?

European beech (Fagus sylvatica L.) is the prevailing tree species of mesic forests in Central Europe. Increasing summer temperatures and decreasing precipitation, as climate change scenarios predict, may, however, negatively influence beech growth and induce a shift to more thermophilous forest communities. Temperatures as expected in the future for western Central Europe are currently found in parts of western Romania. In light of this climate analogy we investigated forest vegetation as an indicator for future vegetation changes in five regions of western Romania representing a climatic gradient. We related species composition to climate variables and examined if tree and understorey species composition respond similarly to the climatic gradient. We further analysed if tree species occurrences correspond with their modelled distance to the rear niche edge. We found evidence for climatic effects on vegetation composition among regions as well as within deciduous and pine forests, respectively. This underlines that vegetation composition is a useful indicator for environmental change. Tree and understorey species compositions were closely linked showing that community-based characterization of forest stands can provide additional information on tree species suitability along environmental gradients. Both, vegetation composition and a climatic marginality index demonstrate the rear niche edge occurrence of beech in the studied sites of Romania and can predict the site suitability for different tree species. While vegetation surveys indicate Quercus petraea to be associated to moderately mesic forests, the marginality index suggested an inner niche position of sessile oak along the climatic gradient. Phytosociological releves that differentiate between subspecies (or microspecies) of sessile oak with differing habitat requirements should be considered to complement national forest inventories and species distribution maps when modelling rear distribution edges. We conclude that climate driven forest vegetation composition in western Romania is a suitable analogon and may indicate future forest development in western Central Europe.

Spatial Autocorrelation Can Generate Stronger Correlations between Range Size and Climatic Niches Than the Biological Signal - A Demonstration Using Bird and Mammal Range Maps.

Species’ geographic ranges could primarily be physiological tolerances drawn in space. Alternatively, geographic ranges could be only broadly constrained by physiological climatic tolerances: there could generally be much more proximate constraints on species’ ranges (dispersal limitation, biotic interactions, etc.) such that species often occupy a small and unpredictable subset of tolerable climates. In the literature, species’ climatic tolerances are typically estimated from the set of conditions observed within their geographic range. Using this method, studies have concluded that broader climatic niches permit larger ranges. Similarly, other studies have investigated the biological causes of incomplete range filling. But, when climatic constraints are measured directly from species’ ranges, are correlations between species’ range size and climate necessarily consistent with a causal link? We evaluated the extent to which variation in range size among 3277 bird and 1659 mammal species occurring in the Americas is statistically related to characteristics of species’ realized climatic niches. We then compared how these relationships differed from the ones expected in the absence of a causal link. We used a null model that randomizes the predictor variables (climate), while retaining their broad spatial autocorrelation structure, thereby removing any causal relationship between range size and climate. We found that, although range size is strongly positively related to climatic niche breadth, range filling and, to a lesser extent, niche position in nature, the observed relationships are not always stronger than expected from spatial autocorrelation alone. Thus, we conclude that equally strong relationships between range size and climate would result from any processes causing ranges to be highly spatially autocorrelated.

Metacommunity structuring in Himalayan streams over large elevational gradients: the role of dispersal routes and niche characteristics

AbstractAimTo examine metacommunity structuring in stream communities over large elevational gradients by disentangling physical and environmental structuring and the importance of different dispersal routes and niche characteristics.LocationHeadwater streams in three catchments in the Hindu‐Kush Himalaya of central and eastern Nepal.MethodsWe explored metacommunity structuring of stream invertebrates (including deconstructed assemblages by niche position and breadth) using a combination of approaches, including the elements of metacommunity structure and distance–decay relationships. We compared the importance of dispersal routes, elevation and local environmental conditions through five distance matrices: Euclidean, topographic, river network, elevational and environmental.ResultsCommunities were structured along the elevational gradient with clear turnover apparent in two catchments, with Clementsian (compartmentalized) and Gleasonian (individualistic) distributions. Local environment played a minor role, and the selected distance matrices (i.e. elevation, three physical distances and environment) varied between catchments and niche groups. Contrary to expectation, specialists were more spatially than environmentally controlled, potentially reflecting dispersal limitation.Main conclusionsIn these physically dominated systems, local environment was overridden by dispersal limitation, particularly when considering specialists. Where barriers were not limiting dispersal, niche sorting along the elevational gradients represented the key structuring force. Overall, our findings reveal the importance of elevation and the spatial arrangement of sites in structuring metacommunities. We emphasize the value of considering physical structuring and spatial extent in modulating species sorting in metacommunities.

Stable isotope-based trophic structure of pelagic fish and jellyfish across natural and anthropogenic landscape gradients in a fjord estuary.

Identifying causes of structural ecosystem shifts often requires understanding trophic structure, an important determinant of energy flow in ecological communities. In coastal pelagic ecosystems worldwide, increasing jellyfish (Cnidaria and Ctenophora) at the expense of small fish has been linked to anthropogenic alteration of basal trophic pathways. However, this hypothesis remains untested in part because baseline description of fish–jellyfish trophic dynamics, and the environmental features that influence them are lacking. Using stable isotopes of carbon (δ13C) and nitrogen (δ15N), we examined spatiotemporal patterns of fish and jellyfish trophic structure in greater Puget Sound, an urbanizing fjord estuary in the NW United States. We quantified niche positions of constituent species, niche widths and trophic overlap between fish and jellyfish assemblages, and several community‐level trophic diversity metrics (resource diversity, trophic length, and niche widths) of fish and jellyfish combined. We then related assemblage‐ and community‐level measures to landscape gradients of terrestrial–marine connectivity and anthropogenic influence in adjacent catchments. Relative niche positions among species varied considerably and displayed no clear pattern except that fish generally had higher δ15N and lower δ13C relative to jellyfish, which resulted in low assemblage‐level trophic overlap. Fish assemblages had larger niche widths than jellyfish in most cases and, along with whole community trophic diversity, exhibited contrasting seasonal patterns across oceanographic basins, which was positively correlated to landscape variation in terrestrial connectivity. In contrast, jellyfish niche widths were unrelated to terrestrial connectivity, but weakly negatively correlated to urban land use in adjacent catchments. Our results indicate that fish–jellyfish trophic structure is highly heterogeneous and that disparate processes may underlie the trophic ecology of these taxa; consequently, they may respond divergently to environmental change. In addition, spatiotemporal variation in ecosystem connectivity, in this case through freshwater influence, may influence trophic structure across heterogeneous landscapes.

A new Navicula (Bacillariophyta) species from low-elevation carbonate springs affected by anthropogenic disturbance

Diatom assemblages in carbonate spring habitats at low elevations, with low discharge, and affected by direct human impacts were studied only recently and in some geographic areas. We describe and characterize the ecology of a new Navicula species from springs with these characteristics within the basin of the River Adige in the south-eastern Alps and Alpine foothills (Province of Verona, Italy). Navicula veronensis sp. nov. is in the group of species around N. cincta but has distinct outline, size, central area, and proximal raphe endings. The availability of data on the distribution of the new species in streams of the Island of Cyprus allowed to quantitatively compare the ecological preferences, niche position, and niche breadth of Navicula veronensis sp. nov. with those of allied species. The new species was found to be characteristic of medium-high conductivity freshwaters, rich in sulphates and chloride, often nitrate enriched and affected by marked discharge fluctuations and seasonal desiccation. Niche position however differed only slightly from those of morphologically-similar species, with the exception of Navicula dealpina that was found to be characteristic of oligotrophic, calcium-bicarbonate rich environments with medium(-low) conductivity. Canonical Correspondence Analysis clearly showed that the most influential environmental variables determining the diatom assemblages of low-elevation carbonate springs affected by anthropogenic disturbance were nitrate enrichment, spring morphology alteration (in particular for water abstraction), and low discharge.

No evidence for larger leaf trait plasticity in ecological generalists compared to specialists

AbstractAimPhenotypic plasticity is hypothesized to contribute to a species’ capacity to occupy broader ranges of conditions and to optimally exploit resource‐rich environments. Although this is supported by case studies of individual species, we do not know whether larger plasticity in functional traits is generally associated with ecological characteristics of species such as their niche breadth or niche position. Here, we test whether there is such a relationship for plasticity in leaf functional traits.LocationCentral Europe.MethodsWe surveyed 110–132 grassland plant species for plasticity in five leaf traits [leaf thickness, leaf greenness, specific leaf area, leaf dry matter content (LDMC) and plant height] and for biomass changes in response to experimental fertilization, shading and waterlogging. Trait plasticity and changes in biomass were compared with species niche characteristics along three environmental axes (light, nutrient and soil moisture) derived from a vegetation‐plot database.ResultsAlthough response of several traits to experimental treatments correlated with niche position and breadth (change in leaf thickness, greenness and biomass in response to fertilization; change in LDMC due to shading; and change in plant height and biomass due to waterlogging), we did not find evidence that species with broader niches or species from resource‐rich environments are more plastic. Ecological generalists even turned out to be less plastic in some traits, including leaf thickness after fertilization and waterlogging. Generalists also displayed smaller plastic response averaged across all five traits (‘composite plasticity’), though the relationship was not statistically significant. This composite plasticity was positively related to absolute change in biomass in all experimental treatments.Main conclusionsOur results suggest that larger species‐level plasticity in leaf traits is not necessarily associated with a capacity to occupy a broader range of environments or with growth in resource‐rich habitats; rather, it may indicate species’ sensitivity to environmental changes.

Exploring species and site contributions to beta diversity in stream insect assemblages.

It was recently suggested that beta diversity can be partitioned into contributions of single sites to overall beta diversity (LCBD) or into contributions of individual species to overall beta diversity (SCBD). We explored the relationships of LCBD and SCBD to site and species characteristics, respectively, in stream insect assemblages. We found that LCBD was mostly explained by variation in species richness, with a negative relationship being detected. SCBD was strongly related to various species characteristics, such as occupancy, abundance, niche position and niche breadth, but was only weakly related to biological traits of species. In particular, occupancy and its quadratic terms showed a very strong unimodal relationship with SCBD, suggesting that intermediate species in terms of site occupancy contribute most to beta diversity. Our findings of unravelling the contributions of sites or species to overall beta diversity are of high importance to community ecology, conservation and bioassessment using stream insect assemblages, and may bear some overall generalities to be found in other organism groups.

Comparing macroecological patterns across continents: evolution of climatic niche breadth in varanid lizards

Macroecological analyses often test hypotheses at the global scale, or among more closely related species in a single region (e.g. continent). Here, we test several hypotheses about climatic niche widths among relatively closely related species that occur across multiple continents, and compare patterns within and across continents to see if they differ. We focus on the lizard genus Varanus (monitor lizards), which occurs in diverse environments in Africa, Asia, and Australia. We address three main questions. 1) How do climatic niche breadths of species on a given niche axis change based on the position of species along that niche axis? (E.g. are species that occur in more extreme environments more narrowly specialized for those conditions?) 2) Are there trade‐offs in niche breadths on temperature and precipitation axes among species, or are niche widths on different axes positively related? 3) Is variation in niche breadths among species explained primarily by within‐locality seasonal variation, or by differences in climatic conditions among localities across the species range? We generate a new time‐calibrated phylogeny for Varanus and test these hypotheses within and between continents using climatic data and phylogenetic methods. Our results show that patterns on each continent often parallel each other and global patterns. However, in many other cases, the strength of relationships can change dramatically among closely related species on different continents. Overall, we found that: 1) species in warmer environments have narrower temperature niche breadths, but there is no relationship between precipitation niche breadth and niche position; 2) temperature and precipitation niche breadths tend to be positively related among species, rather than showing trade‐offs; and 3) within‐locality seasonal variation explains most variation in climatic niche breadths. Some of these results are concordant with previous studies (in amphibians and North American lizards), and might represent general macroecological patterns.

Persist or Produce: A Community Trade-Off Tuned by Species Evenness.

Understanding the effects of biodiversity on community persistence and productivity is key to managing both natural and production systems. Because rare species face greater danger of extinction, species evenness, a measure of how similar abundances are across species in a community, is seen as a key component of biodiversity. However, previous studies have failed to find a consistent association of species evenness with species survival and biomass production. Here we provide a theoretical framework for the relationship among these three elements. We demonstrate that the lack of consistent outcomes is not an idiosyncratic artifact of different studies but can be unified under one common framework. Applying a niche theory approach, we confirm that under demographic stochasticity evenness is a general indicator of the risk of future species extinctions in a community, in accordance with the majority of empirical studies. In contrast, evenness cannot be used as a direct indicator of the level of biomass production in a community. When a single species dominates, as expressed by the constraints imposed by the population dynamics, biomass production depends on the niche position of the dominating species and can increase or decrease with evenness. We demonstrate that high species evenness and an intermediate level of biomass production is the configuration that maximizes the average species survival probability in response to demographic stochasticity.

Responding from that Vantage Point: Field Position and Discursive Strategies of Legitimation in the U.S. Wireless Telegraphy Field

Our study explores the discursive strategies of legitimation that organizations employ as they occupy different positions in an emergent institutional field. By examining both the frame-alignment strategies and the frame targets of two organizations in the U.S. wireless telegraphy field, we show how an organization’s position – and its positional changes over time – affects the discursive strategies it uses to promote or protect its goals in the face of pressure from other field actors. Our results indicate that three distinct field positions – peripheral, central, and niche – are associated with three different legitimation strategies – which we label “robust,” “co-optive,” and “focused” – around which the discursive strategies coalesced. Organizations at the periphery attempt to break in to a field by employing a diverse range of frame-alignment strategies targeted toward a variety of relevant field actors. Those in a central position target fewer actors, but pursue a similar variety of frame-alignment strategies. Those in a niche position use fewer alignment strategies and target a smaller number of field-level actors. Our study enriches the literature on discursive strategies of legitimation by focusing on the ways in which central and non-central actors employ them, and the ways in which these strategies evolve alongside the field itself. More broadly, our work contributes to our understanding of discursive skills required to confront complex institutional pressures. These efforts depend on the interactive nature of discursive strategies from the vantage point of different field positions.

Climatic niche breadth can explain variation in geographical range size of alpine and subalpine plants

ABSTRACTUnderstanding the environmental factors determining the distribution of species with different range sizes can provide valuable insights for evolutionary ecology and conservation biology in the face of expected climate change. However, little is known about what determines the variation in geographical and elevational ranges of alpine and subalpine plant species. Here, we examined the relationship between geographical and elevational range sizes for 80 endemic rhododendron species in China using Spearman’s rank-order correlation. We ran the species distribution model – maximum entropy modelling (MaxEnt) – with 27 environmental variables. The importance of each variable to the model prediction was compared for species groups with different geographical and elevational range sizes. Our results showed that the correlation between geographical and elevational range sizes of rhododendron species was not significant. Climate-related variables were found to be the most important factors in shaping the distributional ranges of alpine and subalpine plant species across China. Species with geographically and elevationally narrow ranges had distinct niche requirements. For geographical ranges, the narrow-ranged species showed less tolerance to niche conditions than the wide-ranged species. For elevational ranges, compared with the wide-ranged species, the narrow-ranged species showed an equivalent niche breadth, but occurred at different niche position along the environmental gradient. Our findings suggest that over large spatial extents the elevational range size can be a complementary trait of alpine and subalpine plant species to geographical range size. Climatic niche breadth, especially the range of seasonal variability, can explain species’ geographical range sizes. Changes in climate may influence the distribution of rhododendrons, with the effects likely being felt most by species with either a narrow geographical or narrow elevational range.

Different hunting strategies of generalist predators result in functional differences.

The morphological, physiological, and behavioural traits of organisms are often used as surrogates for actual ecological functions. However, differences in these traits do not necessarily lead to functional differences and/or can be context-dependent. Therefore, it is necessary to explicitly test whether the surrogates have general ecological relevance. To investigate the relationship between the hunting strategies of predators (i.e., how, where, and when they hunt) and their function, we used euryphagous spiders as a model group. We used published data on the diet composition of 76 spider species based on natural prey and laboratory prey acceptance experiments. We computed differences in the position and width of trophic niches among pairs of sympatrically occurring species. Pairs were made at different classification levels, ranked according to the dissimilarity in their hunting strategies: congeners, confamiliars (as phylogenetic proxies for similarity in hunting strategy), species from the same main class of hunting strategy, from the same supra-class, and from different supra-classes. As for niche position computed from the natural prey analyses, species from the same class differed less than species from different classes. A similar pattern was obtained from the laboratory studies, but the congeners differed less than the species from the same classes. Niche widths were most similar among congeners and dissimilar among species from different supra-classes. Functional differences among euryphagous spiders increased continuously with increasing difference in their hunting strategy. The relative frequency of hunting strategies within spider assemblages can, therefore, influence the food webs through hunting strategy-specific predator-prey interactions.

Exploring stream communities in a tropical biodiversity hotspot: biodiversity, regional occupancy, niche characteristics and environmental correlates

Exploring and describing biodiversity and the mechanisms structuring it is fundamental to advancing ecology. This is particularly pertinent in understudied biogeographical regions, such as the Afrotropics, that are characterised by strong seasonal climatic shifts. We investigated the characteristics of stream biodiversity in the Niger Delta region of Nigeria, a tropical biodiversity hotspot, by examining patterns in 20 stream invertebrate communities across both the wet and dry seasons. For this, we took a multi-faceted approach accounting for the three levels of biodiversity (α, β and γ), including partitioning the nestedness and turnover components of β diversity, regional occupancy-abundance patterns, niche characteristics, and the environmental drivers of community structure. α diversity was low in these streams, with strong turnover between sites leading to high β diversity contributing to regional biodiversity, but there was little variation in communities between seasons. The proportion of sites occupied by taxa declined with increasing niche position, and decreasing niche breadth. Occupancy was predicted well by a combination of these two factors (niche position and breadth), but not mean local abundance, as the abundance-occupancy link was an upper-limit unimodal relationship. On average, community structure was linked more strongly to environmental variables in the wet season. Our findings demonstrate the clear role of spatial, but not temporal, turnover in assemblages, which likely reflects the environmental heterogeneity of this region. This is further supported by the fact that regional occupancy was mostly related to niche characteristics, particularly niche position. We emphasise the importance of continued basic and applied ecological work in this important biogeographic region to enable better protection of its biodiversity.