The history of the Qinghai-Tibetan Plateau and the Himalayas(QTPH)region makes it a'living laboratory'for understanding how the Earth's abiotic evolution has shaped regional biotas.However,no studies to date have attempted to investigate general macro-scale biogeographical patterns and biogeographical affinities of the QTPH terrestrial fauna in a global context.Based on the analyses of the global distributions of QTPH Aphidomorpha species,we examined generalized distribution patterns for them and investigated the biogeographical affinities between the QTPH and other regions.Track analysis and cluster analysis of the global distributions of 298 Aphidomorpha species in the QTPH identified seven generalized biogeographical tracks and eight general distribution patterns.Both approaches detected similarly generalized distribution patterns.Four marginal areas where the generalized tracks intersect,i.e.the eastern Himalayas,the western Himalayas,the Hengduan Mountains,and the northeastern QTPH,were identified as biogeographical nodes.The generalized distribution patterns indicate the biogeographical affinities between the QTPH and other regions and suggest the complex nature of the QTPH fauna.A spatial congruence between the nodes and diversity centres detected by previous studies indicates the four marginal areas have been key areas in fauna evolution as centres for faunal exchange as well as glacial refugia.Based on the biogeographical patterns,the geological history of the QTPH and the evolutionary history of Aphidomorpha,we propose an evolutionary scenario for the evolution of the QTPH aphid fauna in which faunal exchanges,vicariance due to the uplift of geographical barriers,environmental heterogeneity and Quarternary glaciations have shaped the diversity patterns and fauna in the QTPH.

Understanding how species' thermal limits have evolved across the tree of life is central to predicting species' responses to climate change. Here, using experimentally-derived estimates of thermal tolerance limits for over 2000 terrestrial and aquatic species, we show that most of the variation in thermal tolerance can be attributed to a combination of adaptation to current climatic extremes, and the existence of evolutionary 'attractors' that reflect either boundaries or optima in thermal tolerance limits. Our results also reveal deep-time climate legacies in ectotherms, whereby orders that originated in cold paleoclimates have presently lower cold tolerance limits than those with warm thermal ancestry. Conversely, heat tolerance appears unrelated to climate ancestry. Cold tolerance has evolved more quickly than heat tolerance in endotherms and ectotherms. If the past tempo of evolution for upper thermal limits continues, adaptive responses in thermal limits will have limited potential to rescue the large majority of species given the unprecedented rate of contemporary climate change.

Research on the structure of ecological networks suggests that a number of universal patterns exist. Historically, biotic specialization has been thought to increase towards the Equator. Yet, recent studies have challenged this view showing non-conclusive results. Most studies analysing the geographical variation in biotic specialization focus, however, only on the local scale. Little is known about how the geographical variation of network structure depends on the spatial scale of observation (i.e., from local to regional spatial scales). This should be remedied, as network structure changes as the spatial scale of observation changes, and the magnitude and shape of these changes can elucidate the mechanisms behind the geographical variation in biotic specialization. Here we analyse four facets of biotic specialization in host-parasitoid networks along gradients of climatic constancy, classifying the networks according to their spatial extension (local or regional). Namely, we analyse network connectance, consumer diet overlap, consumer diet breadth, and resource vulnerability at both local and regional scales along the gradients of both current climatic constancy and historical climatic change. While at the regional scale none of the climatic variables are associated to biotic specialization, at the local scale, network connectance, consumer diet overlap, and resource vulnerability decrease with current climatic constancy, whereas consumer generalism increases (i.e., broader diet breadths in tropical areas). Similar patterns are observed along the gradient of historical climatic change. We provide an explanation based on different beta-diversity for consumers and resources across the geographical gradients. Our results show that the geographical gradient of biotic specialization is not universal. It depends on both the facet of biotic specialization and the spatial scale of observation.

Adaptive syndromes and their evolutionary constraints represent a powerful construct for understanding plant distributions. However, it is unclear how the species requirements to face multiple stressors promotes syndrome formation and to which abiotic stressors these syndromes show adaptive value over broad geographic scales. We combined local occurrence data from the U.S. Forest Inventory and Analysis (FIA) of 219 angiosperm and 85 gymnosperm species living across the conterminous US with phylogenies and trait data to identify tree syndromes, their evolutionary conservatism, and their adaptive value over broad scales. Factor analyses and evolutionary model selection revealed that trees possess functional trait syndromes that are strongly conserved. Major syndromes at the species level differed between angiosperms and gymnosperms. While the two main syndromes in angiosperms were related to cold and drought‐waterlogging tolerance, in gymnosperms a trade‐off between shade and drought tolerance was the main syndrome followed by a growth‐fire resistance syndrome. Additional RLQ and fourth‐corner approaches revealed that trait syndromes at the community level were broadly similar to those observed at the species level for angiosperms, although this was less clear for gymnosperms. This suggests that syndrome evolution has played an important role on angiosperm distributions, whereas additional ecological factors explain gymnosperm distributions. Importantly, syndromes show adaptive value, as they were geographically associated with several environmental variables showing structure from continental to local scales, being temperature the main abiotic stressor. Our results indicate that across the conterminous US tree species possess clear syndromes that are subjected to strong evolutionary constraints driving tree species and forest community distribution.

How climate affects species distributions is a longstanding question receiving renewed interest owing to the need to predict the impacts of global warming on biodiversity. Is climate change forcing species to live near their critical thermal limits? Are these limits likely to change through natural selection? These and other important questions can be addressed with models relating geographical distributions of species with climate data, but inferences made with these models are highly contingent on non-climatic factors such as biotic interactions. Improved understanding of climate change effects on species will require extensive analysis of thermal physiological traits, but such data are both scarce and scattered. To overcome current limitations, we created the GlobTherm database. The database contains experimentally derived species’ thermal tolerance data currently comprising over 2,000 species of terrestrial, freshwater, intertidal and marine multicellular algae, plants, fungi, and animals. The GlobTherm database will be maintained and curated by iDiv with the aim to keep expanding it, and enable further investigations on the effects of climate on the distribution of life on Earth.

Aims: Phylogenetic niche conservatism (PNC) predicts that closely related species will have similar distributions along major environmental gradients, e.g. temperature. We test this theory by comparing the central tendencies of temperature for selected woody genera, and investigating whether these genera have a similar rank order (sequence) across continents and hemispheres. A strong correlation may indicate niche conservatism, as inherited temperature tolerance would best explain a positive correlation. Location: Peru (Andes) and Nepal (Himalaya). Methods: Elevation and temperature ranges for all species belonging to eight disjunct genera of woody plants were compiled. Central tendencies of congeneric species along the temperature gradient were established by means of reciprocal averaging and weighted average temperature. We correlated the rank order of genera from the Himalaya and Andes, and tested if the order in the Himalaya could predict the order in the Andes, using permutation procedure. Results: Most genera exhibit a bell-shaped or curvilinear pattern with the maximum number of congeneric species in the centre of the temperature range, but some curvilinear responses and monotonic increases are found in Andes. The order of generic optima along the temperature gradient in each region is highly correlated (>0.81), as well as the size of the temperature range and minimum temperature limit (>0.90). Conclusion: The analyses verify the conjecture that the maximum number of congeneric species is found towards the centre of the temperature range of the genus. This may be caused by newly evolving species not dispersing very far from their ancestors and inherent temperature tolerances. Inherent temperature tolerance and covariates such as primary production and soil conditions are the main factors that may explain consistency of the rank order of disjunct genera along temperature gradients between continents and hemispheres. Hence temperature tolerances within a clade are conserved over time and space.

Aim: The species comprising local communities are assembled from the species pool of the region where they are located, and environmental filtering influences which species occupy local communities based on their traits. Latitude and elevation generate two major thermal gradients, and temperature minimum and seasonality can drive community assembly, but few studies have tested if community assembly along both latitudinal and elevational gradients within the same region generates similar patterns of assembly. Here, we test hypotheses on the relations of mean family age (MFA) of angiosperm trees in local communities with environmental temperature and compare the relations between latitudinal and elevational gradients in eastern North America. Location: USA. Method: We used correlation and regression analyses and structure equation modelling approach to assess the relation of MFA to elevation, latitude and climatic variables, which included minimum temperature, temperature seasonality, annual precipitation and precipitation seasonality. Results: The MFA of a local forest community decreased with increasing latitude and elevation for all gradients examined. For each gradient, the slope of the relationship between MFA and latitude or elevation was steeper for forest communities with larger values of MFA than for those with smaller values of MFA, and the standard deviation of MFA decreased with increasing latitude and elevation. MFA decreased significantly with decreasing minimum temperature for both latitudinal and elevational gradients, but the slope of the relationship between MFA and minimum temperature was steeper for elevational gradients than for latitudinal gradients. Minimum temperature had a much stronger relationship with MFA than temperature seasonality for both latitudinal and elevational gradients. Main conclusions: Our results indicate that minimum temperature, rather than temperature seasonality, is a major driver of the pattern of decreasing MFA with increasing latitude and elevation, and the relationship between temperature and MFA is stronger (steeper) for elevational gradients than for latitudinal gradients.

AimSpecies attributes are often used to explain diversity patterns across assemblages/communities. However, repeated species co-occurrences can generate spatial pattern and strong statistical relationships between aggregated attributes and richness in the absence of biological information. Our aim is to increase awareness of this problem.LocationNorth America.MethodsWe generated empirical species richness patterns using two data structures: (1) birds gridded from range maps and (2) tree communities from the US Forest Service's Forest Inventory and Analysis. We analysed richness using linear regression, regression trees, generalized additive models, geographically weighted regression and simultaneous autoregression, with random intrinsic variables' as predictors generated by assigning random numbers to species and calculating averages in assemblages. We then generated simulations in which species with cohesive or patchy distributions are placed with respect to the North American temperature gradient with or without a broad-scale richness gradient. Random intrinsic variables are again used as predictors of richness. Finally, we analysed one simulated scenario with random intrinsic variables as both response and predictor variables.ResultsThe models of bird and tree richness often explained moderate to large proportions of the variance. Regression trees, geographically weighted regression and simultaneous autoregression were very sensitive to the problem; generalized additive models were moderately affected, as was multiple regression to a lesser extent. In the virtual data, the variance explained increased with increasing species co-occurrences, but neither range cohesion, a richness gradient nor spatial autocorrelation in predictors had major impacts on the variance explained. The problem persisted when the response variable was also a random intrinsic variable.Main conclusionsRepeated species co-occurrences can generate strong spurious relationships between richness and aggregated species attributes. It is important to realize that models utilizing assemblage variables aggregated from species-level values, as well as maps illustrating their spatial patterns, cannot be taken at face value.

AbstractUnderstanding how environmental change alters the composition of plant assemblages, and how this in turn affects ecosystem functioning is a major challenge in the face of global climate change. Assuming that values of plant traits express species adaptations to the environment, the trait‐based approach is a promising way to achieve this goal. Nevertheless, how functional traits are related to species’ environmental tolerances and how trait spectra respond to broad‐scale environmental gradients remains largely unexplored. Here, we identify the main trait spectra for US angiosperm trees by testing hypotheses for the relationships between functional traits and species’ environmental tolerances to environmental stresses, as well as quantifying the environmental drivers of assemblage means and variances of these traits. We analyzed >74,000 community assemblages from the US Forest Inventory and Analysis using 12 functional traits, five traits expressing species’ environmental tolerances and 10 environmental variables. Results indicated that leaf traits, dispersal traits, and traits related to stem hydraulics were related to cold or drought tolerance, and their assemblage means were best explained by minimum temperatures. Assemblage means of traits related to shade tolerance (tree growth rate, leaf phosphorus content, and bark thickness) were best explained by aridity index. Surprisingly, aridity index, rather than minimum temperature, was the best predictors of assemblage variances of most traits, although these relationships were variable and weak overall. We conclude that temperature is likely to be the most important driver of functional community structure of North American angiosperm trees by selecting for optimum strategies along the cold and drought stress trade‐off. In turn, water availability primarily affects traits related to shade tolerance through its effect on forest canopy structure and vegetation openness.

Aim Gymnosperms do not follow a latitudinal diversity gradient across the Northern Hemisphere but are influenced by geography at continental scales. Tolerance to physiological aridity is thought to be the main driver of this distribution, yet through evolutionary time conifers have also faced conditions of frost, shade and fire. We tested four predictions to evaluate how environmental stressors and geographical and evolutionary patterns of traits influence conifer distributions: (1) environmental variables related to aridity are most important in explaining geographical patterns of traits; (2) traits responsible for survival in stressful conditions have evolved under a niche conservatism constraint; (3) phylogenetic correlations among traits as the result of complex evolutionary responses to multiple abiotic stressors are widespread; (4) there are parallelisms between spatial trait associations and correlated trait evolution.Location The conterminous United States.Methods We combined conifer occurrences with 10 traits related to drought, freezing, shade and fire. The spatial distribution of traits was mapped and the relationship between environment and the geographical patterns of traits was explored. Niche conservatism was assessed comparing patterns of trait evolution against Brownian motion. We computed geographical and phylogenetic correlations among traits to determine the correspondence between spatial and evolutionary trade-offs.Results (1) Maximum temperature followed by precipitation were the environmental variables that best described the geographical distributions of traits. (2) Most traits contain a phylogenetic signal consistent with niche conservatism: major exceptions being fire-related traits and frost tolerance. (3) Drought and shade tolerances show one of the strongest negative phylogenetic correlations. (4) The drought-shade tolerance trade-off is mirrored at the biogeographical scale.Main conclusions Unlike in angiosperms, cold does not seem to have been a major driver in the evolutionary history of temperate conifers. A strong tradeoff between drought and shade tolerance is the simplest explanation for understanding the current distribution of conifers in North America.

Aims Process-based models are basic tools for predicting the response of forest carbon to future climate change. The models have commonly been tested for their predictions of spatial variation in forest productivity, but much less for their ability to predict temporal variation. Here, we explored methods to test the models with tree rings, using BIOME-BGC as an example. Methods We used net primary productivity (NPP) data and tree rings collected from five major forest types along the altitudinal gradient of Mt. Changbai, northeast China, to test local-parameterized BIOMEBGC model. We first test the model’s predictions of both spatial (Test 1) and temporal changes (Test 2) in productivity. Then we test if the model can detect the climatic factors limiting forest productivity during historical climate change, as revealed by dendroclimatic analyses (Test 3). Important Findings Our results showed that BIOME-BGC could well simulate NPP of five forest types on Mt. Changbai, with an r2 of 0.69 between modeled and observed NPP for 17 plots along the altitudinal gradient (Test 1). Meanwhile, modeled NPP and ring-width indices were correlated and showed similar temporal trends for each forest type (Test 2). While these tests suggest that the model’s predictions on spatial and temporal variation of NPP were acceptable, a further test that relate the correlations of modeled NPP with climate variables to the correlations of ring widths with climate (Test 3) showed that the model did not well identify the climatic factors limiting historical productivity dynamics for some forest types, and thus cannot reliably predict their future. Both dendrochronology and BIOME-BGC showed that forest types differed markedly in the climate factors limiting productivity because of differences in tree species and climate condition, and thus differed in responses to climate change. Our results showed that a successful prediction of spatial NPP patterns cannot assure that BIOME-BGC can well simulate historical NPP dynamics. Further, a correlation between modeled NPP and tree-ring series cannot assure that the limiting climatic factors for productivity have been correctly identified by the model. Our results suggest the necessity to test the temporal predictions of process-based models in a more robust way, and further integration of dendrochronology and biogeochemistry modeling may be helpful for this purpose.

Macroecological and biogeographical studies have assumed that range map data should be used only at coarser grains due to false presences (errors of commission) at small grains. This has been explored using mostly species richness, underrepresenting other potentially informative biodiversity metrics. Here, we evaluated these issues by quantifying the extent to which taxonomic and phylogenetic alpha and beta diversity patterns calculated using anuran range maps at three cell sizes (1×1km, 5×5km, and 10×10km) differ from the patterns calculated based on checklists in 14 protected areas along the southern range of the Brazilian Atlantic Forest. We found that range maps and checklists generated reasonably similar spatial richness patterns in all cell sizes (r≥0.80 in all cases) and slightly weaker, but still correlated alpha phylogenetic diversity patterns (0.78≤r≤0.81). We also found that taxonomic (r≤0.76) and phylogenetic (r≤0.68) beta diversities had lower correlations than alpha spatial patterns. Therefore, range maps have value in documenting alpha biodiversity patterns, as well as beta diversity at more marginal levels, for tropical species at scales relevant to local conservation efforts.

Plant biomass or productivity and the species richness of birds are associated across a range of spatial scales. Species-energy theory is generally assumed to explain these correlations. If true, bird richness should also track productivity temporally, and there should be spatial and temporal relationships between productivity and both bird abundance and bird richness. Using the summer normalized difference vegetation index (NDVI) for 1982-2006 and the North American Breeding Bird Survey, we evaluated the response of avian richness and abundance to interannual changes in plant biomass or productivity. We found positive spatial relationships between richness and NDVI for all 25 years. Temporally, however, richness and NDVI were positively associated at 1579 survey sites and negatively associated at 1627 sites (mean r2 = 0.09). Further, total abundance and NDVI were unrelated spatially (r2 values spanning < 0.01 and 0.03) and weakly related temporally (mean r2 = 0.10). We found no evidence that productivity drives bird richness beyond the spatial correlations, and neither prediction arising from species-energy theory was confirmed. Spatial relationships between productivity and bird richness may thus be largely spurious, arising via covariance between plant biomass or productivity and vegetation structural complexity, and the latter may be driving bird communities. This is consistent with the MacArthurs' classic hypothesis that the vertical profile of foliage drives bird species diversity.

AimThe drivers of tree recruitment over large spatial scales remain unexplored. Here, we ask whether species potential for recruitment and the strength of density-dependent processes, both inferred from species relative abundances, show emerging patterns that can be explained upon the basis of information about climate and functional traits.LocationEastern forests of the USA.MethodsWe document the geographical distributions and magnitudes of seedling recruitment and the strength of density dependence and conspecific density dependence for the forests of the eastern USA spanning >1.2 million km(2) across 88,854 local communities comprising 164 tree species. We also compiled climatic variables and 16 traits representing several important ecological axes of tree functional strategies to assess which factors were most strongly associated with the emerging broad-scale spatial patterns.ResultsStrong geographical variation in the potential for seedling recruitment and a latitudinal change from negative to positive density dependence moving northward were associated with adaptation to seasonal freezing temperatures and seed size. Wood density and leaf nitrogen, in contrast, were related to the magnitude of the negative density dependence and conspecific density dependence, respectively, which were prevalent over most of the region.Main conclusionsOur results provide strong evidence that tree recruitment and the strength of density-dependent processes have broad-scale patterns that can be explained by a few key species functional traits.

Although fungal communities are known to vary along latitudinal gradients, mechanisms underlying this pattern are not well-understood. We used high-throughput sequencing to examine the large-scale distributions of soil fungi and their relation to evolutionary history. We tested the Tropical Conservatism Hypothesis, which predicts that ancestral fungal groups should be more restricted to tropical latitudes and conditions than would more recently derived groups. We found support for this hypothesis in that older phyla preferred significantly lower latitudes and warmer, wetter conditions than did younger phyla. Moreover, preferences for higher latitudes and lower precipitation levels were significantly phylogenetically conserved among the six younger phyla, possibly because the older phyla possess a zoospore stage that is vulnerable to drought, whereas the younger phyla retain protective cell walls throughout their life cycle. Our study provides novel evidence that the Tropical Conservatism Hypothesis applies to microbes as well as plants and animals.

Broad-scale richness gradients are closely associated with temperature and water availability. However, historical and evolutionary processes have also contributed to shape current diversity patterns. In this paper we focus on the potential influences of Pleistocene glaciation and phylogenetic niche conservatism (the tendency for traits to be maintained during diversification) on the tree diversity gradient in Chile, and we quantify its primary climatic correlates. Tree species richness is greatest at mid latitudes, particularly in the Andes and Coastal ranges, and decreases abruptly to the south and north. Regression tree analysis identified annual precipitation and annual temperature as the primary probable drivers of this gradient. Ice cover during the Last Glacial Maximum was also identified as an ‘important’ variable, but the contemporary and historical predictors are strongly collinear. Geographically weighted regression indicated that the relationships between richness and environmental variables vary regionally: the relationship between tree richness and precipitation is stronger in north-central Chile, whereas tree richness and temperature are most strongly associated in south-central Chile. By assigning each species the age of the family to which it belongs and averaging all species in each geographical unit, we also found that species from the oldest families are distributed mainly in mid to high latitudes and species from younger families are distributed mainly at lower latitudes. This pattern is closely associated with annual precipitation. Thus, the ecological component of tree richness follows contemporary climatic gradients of both energy and water, but the aridification of the Atacama Desert was an important driver over evolutionary time. The influence of recent Pleistocene glaciation remains unresolved but it cannot be discounted.