Tropical Elevational Gradient Research Articles

Variation in insulative feather structure in songbirds replacing each other along a tropical elevation gradient.

High‐elevation organisms are expected to evolve physiological adaptations to cope with harsh environmental conditions. Yet, evidence for such adaptive differences, especially compared to closely related lowland taxa occurring along the same elevational gradient, is rare. Revisiting an anecdotal natural history observation by O. Bangs from 1899 and based on new measurements of museum specimens, we confirmed that the high‐elevation hermit wood wren (Henicorhina anachoreta) from the Sierra Nevada de Santa Marta, Colombia, has longer, more insulative feathers on the chest and back, than its lower‐elevation counterpart the grey‐breasted wood wren (H. leucophrys). However, we did not find evidence for the same specializations in subspecies of H. leucophrys that live at high elevations on other elevational gradients in the Colombian Andes, although similar adaptive solutions have arisen in separate mountain systems like the Himalayas. Adaptations in plumage may be associated with the recurrence of elevational species replacements throughout the tropics.

Floral turnover and climate drive seasonal bee diversity along a tropical elevation gradient

AbstractThe contribution of seasonality in species communities to elevational diversity of tropical insects remains poorly understood. We here assessed seasonal patterns and drivers of bee diversity in the Eastern Afromontane Biodiversity Hotspot, Kenya, to understand the contribution of seasonality to elevational biodiversity patterns. Bee species and plant species visited by bees were recorded on 50 study plots in regrowth vegetation across four major seasons along two elevation gradients from 525 to 2530 m above sea level. Bees were sampled by transect walks using sweep nets and aspirators. We examined how local species richness (α‐diversity) and seasonal changes in local species communities (β‐diversity) contribute to species richness across seasons (γ‐diversity) along elevation gradients. Using a multimodel inference framework, we identified the contribution of climate and floral seasonality to elevational patterns in bee diversity. We found that both α‐ and γ‐diversity decreased with elevation. Seasonal β‐diversity decreased with elevation and the high turnover of species across seasons contributed to a considerably higher γ‐ than α‐diversity on study plots. A combination of seasonality in climate and the seasonal turnover of floral resources best explained the seasonality in bee species communities (seasonal β‐diversity). We, therefore, conclude that, despite the more stable, and favorable climatic conditions in the tropics (in comparison to temperate regions), climatic seasonality and its influence on bees' floral resources largely determined seasonal patterns of bee species diversity along elevation gradients on tropical mountains.

Contrasting functional responses of non-native invasive species along a tropical elevation gradient

One hypothesized invasion strategy (“try-harder”) predicts that invaders exhibit functional traits that are better adjusted to the environment than native species. Alternatively, the “join-the-locals” hypothesis predicts trait convergence between invasive and native species due to environmental filtering with increasing resource limitation. We hypothesized that invasions strategies shift from “try-harder” to “join-the-locals” with increasing elevation. We used an elevational gradient to detect possible trait convergences between alien invaders and native plant species in Asteraceae, Fabaceae and Poaceae. We found a significant trait convergence with elevation only in Asteraceae, suggesting a species-specific pattern, but also an important phenotypic variability of the alien invader. This supports the idea that the more resource-limited the environment, the more it filters out traits substantially diverging from the locally-adapted native community, thereby entailing a shift from “try-harder” to “join-the-locals” strategies. The invasive grass was also more acquisitive but did not exhibit any relation to the native community, supporting the “try-harder” hypothesis. The size of the invasive Fabaceae species decreased with elevation, mirroring the native Fabaceae species, but not the overall native community. Including more replicates and a thorough quantification of environmental conditions, offers a promising avenue for improving the understanding the seemingly idiosyncrasies of invasion pathways.

Environmental variation associated with topography explains butterfly diversity along a tropical elevation gradient

AbstractFew studies have evaluated the role of topography on the diversity patterns of biological communities along elevation gradients. We evaluated the influence of microclimate and vegetation structure associated with topographic variation on the richness and composition of species of different families of butterflies on a mountain located in a dry enclave (Chicamocha River Canyon) in the northern Andes, Colombia. We captured butterflies over four months at 18 elevations (300 to 1500 m a.s.l.) in two topographic positions (riverbed and hillslope) using an entomological net and traps baited with fermented fruit. In general, butterfly richness increased with elevation in both topographic positions. However, the richness–elevation relationship changed with butterfly family. The riverbed and hillslope sites host different assemblages of butterflies, and this pattern that was consistent for most families. In the riverbed, two sets of species are recognized along the elevation gradient (one below 700 m a.s.l. and the other above 1000 m a.s.l.), mainly owing to species replacement. On the hillslopes, there was no clear pattern of grouping associated with elevation. Microclimate differences between the riverbed and hillslope sites along the elevation gradient were related to the vegetation structure and explained the variation in butterfly species composition. Our results highlight the role of topography not only by explaining the response of species richness and composition to environmental variation determined by elevation, but also as a factor that must be considered in the planning and management of biodiversity conservation in the mountains.Abstract in Spanish is available with online material.

Taxonomic scale dependency of Bergmann’s patterns: a cross-scale comparison of hawkmoths and birds along a tropical elevational gradient

AbstractBergmann’s rule predicts a larger body size for endothermic organisms in colder environments. The contrasting results from previous studies may be due to the differences in taxonomic (intraspecific, interspecific and community) and spatial (latitudinal vs elevational) scales. We compared Bergmann’s patterns for endotherms (Aves) and ectotherms (Lepidoptera: Sphingidae) along the same 2.6 km elevational transect in the eastern Himalayas. Using a large data spanning 3,302 hawkmoths (76 morpho-species) and 15,746 birds (245 species), we compared the patterns at the intraspecific (hawkmoths only), interspecific and community scales. Hawkmoths exhibited a positive Bergmann’s pattern at the intraspecific and abundance-weighted community scale. Contrary to this, birds exhibited a strong converse Bergmann’s pattern at interspecific and community scales, both with and without abundance. Overall, our results indicate that incorporation of information on intraspecific variation and/or species relative abundances influences the results to a large extent. The multiplicity of patterns at a single location provides the opportunity to disentangle the relative contribution of individual- and species-level processes by integrating data across multiple nested taxonomic scales for the same taxa. We suggest that future studies of Bergmann’s patterns should explicitly address taxonomic and spatial scale dependency, with species relative abundance and intraspecific trait variation as essential ingredients especially at short elevational scales.

Abiotic and biotic drivers of functional diversity and functional composition of bird and bat assemblages along a tropical elevation gradient

AbstractAimThe identification of the mechanisms determining spatial variation in biological diversity along elevational gradients is a central objective in ecology and biogeography. Here, we disentangle the direct and indirect effects of abiotic drivers (climatic conditions, and land use) and biotic drivers (vegetation structure and food resources) on functional diversity and composition of bird and bat assemblages along a tropical elevational gradient.LocationSouthern slopes of Mt. Kilimanjaro, Tanzania, East Africa.MethodsWe counted birds and recorded bat sonotypes on 58 plots distributed in near‐natural and anthropogenically modified habitats from 700 to 4,600 m above sea level. For the recorded taxa, we compiled functional traits related to movement, foraging and body size from museum specimens and databases. Further, we recorded mean annual temperature, precipitation, vegetation complexity as well as the number of fruits, flowers, and insect biomass as measures of resource availability on each study site.ResultsUsing path analyses, we found similar responses of bird and bat functional diversity to the variation in abiotic and biotic drivers along the elevational gradient. In contrast, the functional composition of both taxa showed distinct responses to abiotic and biotic drivers. For both groups, direct temperature effects were most important, followed by resource availability, precipitation and vegetation complexity.Main ConclusionsOur findings indicate that physiological and metabolic constraints imposed by temperature and resource availability determine the functional diversity of bird and bat assemblages, whereas the composition of individual functional traits is driven by taxon‐specific processes. Our study illustrates that distinct filtering mechanisms can result in similar patterns of functional diversity along broad environmental gradients. Such differences need to be taken into account when it comes to conserving the functional diversity of flying vertebrates on tropical mountains.

Determinism and stochasticity in the spatial–temporal continuum of ecological communities: the case of tropical mountains

Ecological communities are assembled in a spatial–temporal continuum. However, we still have a poor understanding of the relative importance of different mechanisms structuring community composition (i.e. beta‐diversity) in space and time. In this study, we start by introducing a conceptual model that capitalizes upon the core‐occasional species concept to predict that the assembly process in tropical mountains is driven by the deterministic turnover of core species in space via habitat sorting, but the turnover of occasional species through time via stochastic events of colonization and local extinctions. We then propose a general analytical framework that allows assessing these predictions by partitioning the total variance of a species‐by‐site‐by‐time matrix (i.e. total beta‐diversity) among its purely spatial (variation in space independent of time), purely temporal (variation in time independent of space) and spatiotemporal (i.e. variation across different sites across different moments in time) components. Through simulation models, we provided theoretical support that the proposed analytical framework is suitable to test the predictions derived from our conceptual model. We then used this framework to identify general patterns and quantify the relative importance of processes underlying the spatial and temporal organization of ten distinct insect metacommunities along a tropical elevational gradient. As predicted, we found that, across taxa, spatial beta‐diversity was mainly explained by environmental variation alone: a pattern that indicates the spatial turnover of core species. In contrast, temporal beta‐diversity could not be distinguished from the expectation of null models where communities are simply represented by random draws from species pools: a pattern that indicates a temporal turnover of occasional species within communities. Taken together, our findings illustrate how our conceptual model and quantitative framework can articulate a better understanding of community assembly in space and time.

Temperature and productivity distinctly affect the species richness of ectothermic and endothermic multitrophic guilds along a tropical elevational gradient.

The diversity of endotherms and ectotherms may be differently affected by ambient temperature and net primary productivity (NPP). Additionally, little is known about how these drivers affect the diversity of guilds of different trophic levels. We assessed the relative role of temperature and NPP in multitrophic guilds of ectothermic (arthropods: ants, ground beetles, spiders, and harvestmen) and endothermic (large mammals) animals along a tropical elevational gradient. We sampled arthropods at eight elevation belts and large mammals at 14 elevation belts in Atlantic rainforest (ranging from 600 to 2450m.a.s.l.) of Itatiaia National Park, Southeast Brazil. Overall arthropod species richness was more associated with temperature than overall large-mammal species richness, while the latter was more associated with NPP. When separated into trophic guilds, we found that the species richness associated with NPP increased across arthropod trophic levels from herbivores to predators. Conversely, although NPP influenced large-mammal herbivore species richness, its effects did not seem to accumulate across large-mammal trophic levels since the species richness of large-mammal omnivores was more associated with temperature and none of the variables we studied influenced large-mammal predators. We suggest that thermal physiological differences between ectotherms and endotherms are responsible for the way in which arthropods and large mammals interact with or are constrained by the environment. Furthermore, the inconsistency regarding the role of temperature and NPP on species richness across multitrophic guilds of ectotherms and endotherms could indicate that thermal physiological differences might also interfere with energy use and flux in the food web.

Patterns and drivers of leaf‐litter ant diversity along a tropical elevational gradient in Mexico

AbstractAimGiven their high environmental variation over relatively short distances, mountains represent ideal systems for evaluating potential factors shaping diversity gradients. Despite a long‐standing interest in ecological gradients, ant diversity patterns and their related mechanisms occurring on mountains are still not well understood. Here, we (i) describe species diversity patterns (α and β) of leaf‐litter ants along the eastern slope of Cofre de Perote in Veracruz, Mexico; and (ii) evaluate climatic and spatial factors in determining these patterns.LocationVeracruz, Mexico.TaxonLeaf‐litter ants.MethodsWe sampled 320 m2 of leaf litter spread across eight equally spaced sites from sea level to 3500 m of elevation. We used regression models to predict α‐diversity patterns with climatic (temperature and precipitation) and spatial (geometric constraints) variables. We also assessed, through multiple regression based on distance matrices (MRM), the relative importance of habitat filtering and dispersal limitations for shaping total dissimilarity (βsor), turnover (βsim) and nestedness (βnes).ResultsA hump‐shaped pattern was observed in the α‐diversity. This pattern is best explained by the temperature gradient. β‐diversity showed a nonlinear pattern along the elevational gradient with total dissimilarity and turnover components better explained by habitat filtering (i.e. temperature distances). Turnover had higher contribution to total dissimilarity rather than the nestedness component.Main conclusionsThe significance effect of temperature on both α‐ and β‐diversity patterns reinforces its widespread importance in shaping litter ant diversity patterns across elevational gradients. The hump‐shaped pattern in species richness is probably the result of harsh abiotic conditions at the base and the top of the mountain combined with biotic attrition in lowland sites. The niche specialization of ant species in their optimal thermal zones may explain total dissimilarity and ant species replacement along the studied gradient. Taken all together, these results suggest a high relevance of temperature‐driven mechanisms in the origin and maintenance of the biodiversity of such insects and probably another ectothermic taxa.

Variation of Foliar Calcium and Magnesium in Six Fern Species at Different Elevations

Several efforts have been made to understand nutrient ecology worldwide. However, Ca and Mg have received less attention, despite their function in important biological processes of plants, such us growth and photosynthesis. Few studies focus on fern nutrient ecology of foliar Ca and Mg. Moreover, none has investigated the variation of these elements along elevational gradients. Herein, we analysed if there were differences of the foliar Ca and Mg contents of six species of ferns along a tropical elevational gradient: Adiantum humile, Cyathea tortuosa, Cyclodium meniscioides, Danaea moritziana, Maxonia apiifolia, and Thelypteris biformata. We found significant differences at the interspecific and intraspecific level variation of foliar Ca and Mg contents at each elevation. In terms of the relationship between elevation and nutrient content, we found that two species showed contrasting trends of foliar Ca with elevation. Content of Ca decreased with elevation in Adiantum humile, while it increased in Maxonia apiifolia. Regarding Mg, it decreased with elevation in Adiantum humile, Thelypteris biformata and Maxonia apiifolia. However, these results were not statistically supported. An exhaustive sampling effort will provide insight on variation of foliar Ca and Mg along tropical elevation gradients and the factors influencing patterns of variation.

Climate implications on forest above- and belowground carbon allocation patterns along a tropical elevation gradient on Mt. Kilimanjaro (Tanzania)

Tropical forests represent the largest store of terrestrial biomass carbon (C) on earth and contribute over-proportionally to global terrestrial net primary productivity (NPP). How climate change is affecting NPP and C allocation to tree components in forests is not well understood. This is true for tropical forests, but particularly for African tropical forests. Studying forest ecosystems along elevation and related temperature and moisture gradients is one possible approach to address this question. However, the inclusion of belowground productivity data in such studies is scarce. On Mt. Kilimanjaro (Tanzania), we studied aboveground (wood increment, litter fall) and belowground (fine and coarse root) NPP along three elevation transects (c. 1800–3900 m a.s.l.) across four tropical montane forest types to derive C allocation to the major tree components. Total NPP declined continuously with elevation from 8.5 to 2.8 Mg C ha−1 year−1 due to significant decline in aboveground NPP, while fine root productivity (sequential coring approach) remained unvaried with around 2 Mg C ha−1 year−1, indicating a marked shift in C allocation to belowground components with elevation. The C and N fluxes to the soil via root litter were far more important than leaf litter inputs in the subalpine Erica forest. Thus, the shift of C allocation to belowground organs with elevation at Mt. Kilimanjaro and other tropical forests suggests increasing nitrogen limitation of aboveground tree growth at higher elevations. Our results show that studying fine root productivity is crucial to understand climate effects on the carbon cycle in tropical forests.

Ecological drivers of avian community assembly along a tropical elevation gradient

Community assembly theory hypothesizes that two main niche‐based processes act to shape composition and organization of biological assemblages: abiotic filtering and biological interactions. Here, we conducted repeated surveys of bird abundance along an undisturbed elevational gradient in the tropical Andes to investigate 1) signals of deterministic processes driving community assembly and 2) potential mechanisms by which these forces operate (temperature, habitat complexity, fruit and insect availability), while correcting for imperfect detection and modeling species abundances with N‐mixture models. We observed strong signals of abiotic filtering driving functionally and phylogenetically clustered assemblages towards higher elevations, and a weaker signal of limiting similarity resulting in few overdispersed assemblages at lower elevations. Whereas the decay in species richness with increasing elevation was explained by temperature, trait and phylogenetic dispersion were explained by both temperature and vegetation structure, implying that an interplay of abiotic and biotic mechanisms determines abundance‐based community structure in our montane assemblages. Interestingly, trait and phylogenetic dispersion consistently decreased until ~3000 m but increased above this elevation, highlighting a potential role of competition in resource‐scarce habitats. Combined, our findings suggest abiotic filters are still the main process shaping montane biotas across elevations, whereas resource availability might act locally upon assemblages further modifying them. Our study challenges recent studies in tropical mountains that suggest that biotic filters are a stronger force than abiotic filters in shaping tropical montane assemblages, and exemplifies how accounting for imperfect detection might overcome potential biases in detecting environmental filtering signals in community assembly studies.

Interactive impacts of climate change and land-use change on the demography of montane birds.

Climate change and habitat degradation are amongst the two greatest threats to biodiversity. Together, they can interact to imperil species. However, how climate change and land-use change jointly affect the demographic vital rates that underpin population viability remains unknown. Here, using long-term data on birds from the increasingly degraded and rapidly warming Himalayas, we show that survival trends over time are linked to species' elevational ranges in primary, but not in selectively logged forest. In primary forest, populations at their cold-edge elevational range limit show increases in survival rates over time, whereas those at their warm-edge elevational range limit suffer survival declines. This pattern is consistent with species tracking favorable climatic conditions over time, leading to improved demographic outcomes at progressively higher elevations with climate change, which in turn lead to upslope range shifts. In logged forest, however, survival rates remain relatively constant over time. This suggests that, in response to climate change in the long term, individuals of the same species can maintain demographic vital rates in higher-elevation primary forest, but not in logged forest. This is the first demonstration of how two of the most disruptive anthropogenic influences on biodiversity interact to threaten survivorship in natural populations. Ignoring interactions between climate change and land-use change can potentially undermine accurate forecasting of the future of species in an increasingly warm and degraded world. Importantly, large tracts of well-protected primary forests across Earth's tropical elevational gradients may be essential to enable tropical montane species to persist in the face of climate change.

Elevational gradients of reptile richness in the southern Western Ghats of India: Evaluating spatial and bioclimatic drivers

AbstractExploring elevational patterns in species richness and their underlying mechanisms is a major goal in biogeography and community ecology. Reptiles can be powerful model organisms to examine biogeographical patterns. In this study, we examine the elevational patterns of reptile species richness and test a series of hypotheses that may explain them. We sampled reptile communities along a tropical elevational gradient (100–1,500 m a.s.l.) in the Western Ghats of India using time‐constrained visual encounter surveys at each 100‐m elevation zone for 3 years. First, we investigated species richness patterns across elevation and the support of mid‐domain effect and Rapoport's rule. Second, we tested whether a series of bioclimatic (temperature and tree density) and spatial (mid‐domain effect and area) hypotheses explained species richness. We used linear regression and AICc to compare competing models for all reptiles, and each of the subgroups: snakes, lizards, and Western Ghats’ endemics. Overall reptile richness and lizard richness both displayed linear declines with elevation, which was best explained by temperature. Snake richness and endemic species richness did not systematically vary across elevation, and none of the potential hypotheses explained variation in them. This is the first standardized sampling of reptiles along an elevational gradient in the Western Ghats, and our results agree with the global view that temperature is the primary driver of ectotherm species richness. By establishing strong reptile diversity–temperature associations across elevation, our study also has implications for the impact of future climate change on range‐restricted species in the Western Ghats.

Environmental determinants of leaf litter ant community composition along an elevational gradient

AbstractAnt communities are extremely diverse and provide a wide variety of ecological functions in tropical forests. Here, we investigated the abiotic factors driving ant composition turnover across an elevational gradient at Mont Itoupé, French Guiana. Mont Itoupé is an isolated mountain whose top is covered by cloud forests, a biogeographical rarity that is likely to be threatened according to climate change scenarios in the region. We examined the influence of six soil, climatic, and LiDAR‐derived vegetation structural variables on leaf litter ant assembly (267 species) across nine 0.12‐ha plots disposed at three elevations (ca. 400, 600, and 800m asl). We tested (a) whether species cooccurring within a same plot or a same elevation were more similar in terms of taxonomic, functional, and phylogenetic composition, than species from different plots/elevations, and (b) which environmental variables significantly explained compositional turnover among plots. We found that the distribution of species and traits of ant communities along the elevational gradient was significantly explained by a turnover of environmental conditions, particularly in soil phosphorus and sand content, canopy height, and mean annual relative humidity of soil. Our results shed light on the role exerted by environmental filtering in shaping ant community assembly in tropical forests. Identifying the environmental determinants of ant species distribution along tropical elevational gradients could help predicting the future impacts of global warming on biodiversity organization in vulnerable environments such as cloud forests.

Response of tree diversity and community composition to forest use intensity along a tropical elevational gradient

AbstractQuestionLand‐use change and intensification are currently the most pervasive threats to tropical biodiversity. Yet, their effects on biodiversity change with elevation are unknown. Here, we examine how tree diversity and community composition vary with elevation and how the effects of forest use intensity on tree diversity and community composition change within elevations.LocationEastern slopes of the Cofre de Perote mountain, state of Veracruz, Mexico.MethodsWe assessed tree diversity and composition using a sampling design in which elevation was crossed with three levels of forest use intensity: old‐growth, degraded, and secondary forests. We established 120 20 m × 20 m forest plots, located at eight sites between 0 m and 3,545 m. At each site, five replicate plots were inventoried for each level of forest use intensity.ResultsOur analyses revealed an interactive effect between elevation and forest use intensity affecting tree diversity and community composition along the elevational gradient. Contrasting effects of forest use intensity within elevation resulted in tree diversity following a low‐plateau pattern for old‐growth and a bimodal pattern for degraded and secondary forests. Along the entire elevational gradient, there were 217 tree species distributed within 154 genera and 80 families. Species accumulation curves revealed that forests at 0 m and 1,500 m elevation showed differences in species richness among forest use intensities. In contrast, species richness did not differ between old‐growth forest and the other forest use intensities in five of the eight studied elevations. In terms of community composition, secondary forests differed from old‐growth and degraded forests.ConclusionOur results suggest that the interactive effects of elevation and forest use intensity change tree diversity patterns and community composition along a tropical elevational gradient. Degraded forests were similar to old‐growth forests in terms of species diversity and composition, suggesting that they may act as a safeguard of tree diversity in human‐dominated tropical landscapes.

Projected impacts of climate change on functional diversity of frugivorous birds along a tropical elevational gradient

Climate change forces many species to move their ranges to higher latitudes or elevations. Resulting immigration or emigration of species might lead to functional changes, e.g., in the trait distribution and composition of ecological assemblages. Here, we combined approaches from biogeography (species distribution models; SDMs) and community ecology (functional diversity) to investigate potential effects of climate-driven range changes on frugivorous bird assemblages along a 3000 m elevational gradient in the tropical Andes. We used SDMs to model current and projected future occurrence probabilities of frugivorous bird species from the lowlands to the tree line. SDM-derived probabilities of occurrence were combined with traits relevant for seed dispersal of fleshy-fruited plants to calculate functional dispersion (FDis; a measure of functional diversity) for current and future bird assemblages. Comparisons of FDis between current and projected future assemblages showed consistent results across four dispersal scenarios, five climate models and two representative concentration pathways. Projections indicated a decrease of FDis in the lowlands, an increase of FDis at lower mid-elevations and little changes at high elevations. This suggests that functional dispersion responds differently to global warming at different elevational levels, likely modifying avian seed dispersal functions and plant regeneration in forest ecosystems along tropical mountains.

Seasonal shifts of biodiversity patterns and species’ elevation ranges of butterflies and moths along a complete rainforest elevational gradient on Mount Cameroon

AbstractAimTemporal dynamics of biodiversity along tropical elevational gradients are unknown. We studied seasonal changes of Lepidoptera biodiversity along the only complete forest elevational gradient in the Afrotropics. We focused on shifts of species richness patterns, seasonal turnover of communities and seasonal shifts of species’ elevational ranges, the latter often serving as an indicator of the global change effects on mountain ecosystems.LocationMount Cameroon, Cameroon.TaxonButterflies and moths (Lepidoptera).MethodsWe quantitatively sampled nine groups of Lepidoptera by bait‐trapping (16,800 trap‐days) and light‐catching (126 nights) at seven elevations evenly distributed along the elevational gradient from sea level (30 m a.s.l.) to timberline (2,200 m a.s.l.). Sampling was repeated in three seasons.ResultsAltogether, 42,936 specimens of 1,099 species were recorded. A mid‐elevation peak of species richness was detected for all groups but Eupterotidae. This peak shifted seasonally for five groups, most of them ascending during the dry season. Seasonal shifts of species’ elevational ranges were mostly responsible for these diversity pattern shifts along elevation: we found general upward shifts in fruit‐feeding butterflies, fruit‐feeding moths and Lymantriinae from beginning to end of the dry season. Contrarily, Arctiinae shifted upwards during the wet season. The average seasonal shifts of elevational ranges often exceeded 100 m and were even several times higher for numerous species.Main conclusionsWe report seasonal uphill and downhill shifts of several lepidopteran groups. The reported shifts can be driven by both delay in weather seasonality and shifts in resource availability, causing phenological delay of adult hatching and/or adult migrations. Such shifts may lead to misinterpretations of diversity patterns along elevation if seasonality is ignored. More importantly, considering the surprising extent of seasonal elevational shifts of species, we encourage taking account of such natural temporal dynamics while investigating the global climate change impact on communities of Lepidoptera in tropical mountains.

Elevational filtering and the evolution of planthoppers (Hemiptera, Fulgoromorpha) in Papua New Guinea

AbstractAlong elevational gradients, phylogenetic relatedness patterns constitute a considerable source of information and may shed light on ecological processes that structure communities. This study focuses on community phylogenetic structure of planthoppers, specifically the species‐rich and abundant Fulgoromorpha families (Hemiptera, Auchenorrhyncha), Cixiidae and Derbidae + Achilidae, along an elevational gradient on Mount Wilhelm (Papua New Guinea). In order to assess the factors driving planthoppers community composition, we recorded abundance data for planthoppers species at each elevation and we generated a molecular phylogeny of the local species, using Bayesian inference. We analyzed 168 individuals representing 59 local morphospecies. Using a fully resolved and well‐supported phylogeny, we then investigated the phylogenetic structure of the communities by performing a Spatial Analysis of Community Diversity. We show that Cixiidae are phylogenetically clustered along the elevational gradient, whereas Derbidae + Achilidae harbor a random structure, suggesting that local adaptation to elevation shapes community structure of Cixiidae, but not that of Derbidae + Achilidae. Our findings highlight the importance of phylogenies in the study of tropical elevational gradients.

Biotic interactions are the dominant drivers of phylogenetic and functional structure in bird communities along a tropical elevational gradient

AbstractUnderstanding how biotic and abiotic interactions influence community assembly and composition is a fundamental goal in community ecology. Addressing this issue is particularly tractable along elevational gradients in tropical mountains that feature substantial abiotic gradients and rates of species turnover. We examined elevational patterns of avian community structure on 2 mountains in Malaysian Borneo to assess changes in the relative strength of biotic interactions and abiotic constraints. In particular, we used metrics based on (1) phylogenetic relatedness and (2) functional traits associated with both resource acquisition and tolerance of abiotic challenges to identify patterns and causes of elevational differences in community structure. High elevation communities were composed of more phylogenetically and functionally similar species than would be expected by chance. Resource acquisition traits, in particular, were clustered at high elevations, suggesting low resource and habitat diversity were important drivers of those communities. Traits typically associated with tolerance of cold temperatures and low atmospheric pressure showed no elevational patterns. All traits were neutral or overdispersed at low elevations suggesting an absence of strong abiotic filters or an increased influence of interspecific competition. However, relative bill size, which is important for thermoregulation, was larger in low elevation communities, suggesting abiotic factors were also influential there. Regardless of metric, clustered and neutral communities were more frequent than overdispersed communities overall, implying that interspecific competition among close relatives may not be a pervasive driver of elevational distribution and community structure of tropical birds. Overall, our analyses reveal that a diverse set of predominantly biotic factors underlie elevational variation in community structure on tropical mountains.