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Question: Global-scale forest censuses provide an opportunity to understand diversification processes in woody plant communities. Based on the climatic or geographic filtering hypotheses associated with tropical niche conservatism and dispersal limitation, we analysed phylogenetic community structures across a wide range of biomes and evaluated to what extent region-specific processes have influenced large-scale diversity patterns of tree species communities across latitude or continent. Location: Global. Methods: We generated a data set of species abundances for 21,379 angiosperm woody plants in 843 plots worldwide. We calculated net relatedness index (NRI) for each plot, based on a single global species pool and regional species pools, and phylogenetic β-diversity (PBD) between plots. Then, we explored the correlations of NRI with climatic and geographic variables, and clarified phylogenetic dissimilarity along geographic and climatic differences. We also compared these patterns for South America, Africa, the Indo-Pacific, Australia, the Nearctic, Western Palearctic and Eastern Palearctic. Results: NRI based on a global-scale species pool was negatively associated with precipitation and positively associated with Quaternary temperature change. PBD was positively associated with geographic distance and precipitation difference between plots across tropical and extratropical biomes. Moreover, phylogenetic dissimilarity was smaller in extratropical regions than in regions including the tropics, although temperate forests of the Eastern Palearctic showed a greater dissimilarity within extratropical regions. Conclusions: Our findings support predictions of the climatic and geographic filtering hypotheses. Climatic filtering (climatic harshness and paleoclimatic change) relative to tropical niche conservatism played a role in sorting species from the global species pool and shaped the large-scale diversity patterns, such as the latitudinal gradient observed across continents. Geographic filtering associated with dispersal limitation substantially contributed to regional divergence of tropical/extratropical biomes among continents. Old, long-standing geographic barriers and recent climatic events differently influenced evolutionary diversification of angiosperm tree communities in tropical and extratropical biomes.

Aim: Large-scale biodiversity patterns are often discussed in the context of 'out of the tropics' (OTT) dynamics and/or tropical niche conservatism (TNC), but empirical evidence of these processes remains very limited. The aim of this study was to infer diversification processes and mechanisms of Cenozoic diversity dynamics using woody angiosperms. Location: East Asian continental islands and global. Time period: Cenozoic. Major taxa studied: Woody plants. Methods: We compiled Cenozoic fossil and modern records for woody angiosperm genera to reconstruct biodiversity patterns. To evaluate the relative importance of TNC and OTT, we investigated extinction/survival patterns and latitudinal range dynamics for each genus, in combination with their clade age (mean family age), cold tolerance and per-genus species richness. Results: We found diversity decreasing with latitude in modern-day flora, but not in the warmer periods of the Neogene and Palaeogene. The percentage of genera surviving decreased with latitude through the Cenozoic. Older genera with less cold tolerance and/or species-poor genera went extinct locally at high latitudes in response to post-Pliocene global cooling. Evolutionarily younger temperate genera dispersed from the extratropics to lower latitudes and the Southern Hemisphere after the Neogene. Main conclusions: The latitudinal diversity gradient (LDG) has rapidly steepened post-Pliocene through: (a) selective extinction in higher latitudes of old, less-diversified tropical genera with low freezing tolerance, and (b) equatorward distributional shift of temperate genera. Both these processes were driven by the high-latitude cooling. Such major roles of TNC and OTT, wherein temperate genera in the Northern Hemisphere expanded through the tropics into higher latitudes of the Southern Hemisphere across climatic boundaries without losing their temperate presence, are in contrast to OTT processes in marine systems. Cenozoic patterns of terrestrial woody angiosperm biodiversity indicate the importance of TNC and high-latitude processes, including the extinction of tropical genera and range contraction or shift of temperate genera.

To examine the influence of climatic extinction filtering during the last glacial maximum (LGM; c. 18,000 yr bp) and of the subsequent recolonization of forest faunas on contemporary assemblage composition in southern African forests. South Africa, Mozambique, Swaziland, Zimbabwe. Data comprised presence/absence by quarter-degree grid cell for forest-dependent and forest-associated birds, non-volant mammals and frogs. Twenty-one forest subregions were assigned to one of three previously identified forest types: Afrotemperate, scarp, and Indian Ocean coastal belt. Differences among forest types were examined through patterns and gradients of species richness and endemism, assemblage similarity, species turnover, and coefficients of species dispersal direction. The influence of contemporary environment on assemblage composition was investigated using partial canonical correspondence analysis. Several alternative biogeographical hypotheses for the recolonization of forest faunas were tested. Afrotemperate faunas are relatively species-poor, have low species turnover, and are unsaturated and infiltrated by generalist species. In northern and central regions, communities are supplemented by recolonization from scarp forest refugia, and among frogs by autochthanous speciation in localized refugia. Scarp faunas are relatively species-rich, contain many forest-dependent species, have high species turnover, and overlap with coastal and Afrotemperate faunas. Coastal forests are relatively species-rich with high species turnover. Afrotemperate communities were affected most by climatic extinction filtering events. Scarp forests were Afrotemperate refugia during the LGM and are a contemporary overlap zone between Afrotemperate and coastal forest. Coastal faunas derive from post-LGM colonization along the eastern seaboard from tropical East African refugia. The greatest diversity is achieved in scarp and coastal forest faunas in northern KwaZulu-Natal province. This historical centre of diversity has influenced the faunal diversity of nearly all other forests in South Africa. The response of vertebrate taxa to large-scale, historical processes is dependent on their relative mobility: forest birds best illustrate patterns resulting from post-glacial faunal dispersal, while among mammals and frogs the legacy of climatic extinction filtering remains stronger.

Question: What is the relative importance of area- and edge-effects on woody seedling diversity in old Afromontane forest fragments? Location: Mistbelt Afromontane forests, KwaZulu-Natal midlands, South Africa. Methods: Woody seedling abundance and species richness in 590 1-m2 plots were sampled at the forest edge (< 10 m from the edge) and interior in 31 old (> 60 a) Afromontane forest fragments (0.05 – 328.5 ha) with closed edges in an ancient grassland matrix. Results: Unlike young (< 20 a) Amazonian fragments, there was no edge- or area-effect on sample plot seedling density and species richness, although these increased significantly with increasing herb cover (less disturbance). Seedling density, but not species richness, declined significantly with herbivory of seedlings, regardless of forest size or plot location. Seedling community composition and richness did not differ significantly between the edge and interior of forests across the range of forest sizes (i.e. no edge-effect). Community composition was nested with small forests retaining a subset of the seedling flora of larger forests. Overall, cumulative seedling species richness increased with forest area (i.e. area-effect). Conclusions: Holocene climatic extinction filtering events and area-dependent species relaxation have potentially selected for tree species with convergent life histories adapted to local fragmentation-effects. Stable environmental conditions at old edges in these naturally fragmented forests cause similar regeneration conditions and seedling species composition between edge and interior. Consequently, seedling density and species richness are controlled more by response to gradients of local disturbance (habitat area, herb cover, herbivory) than by proximity to the edge. Large patches (> 50 ha) with intact edges had the highest tree seedling diversity and are a conservation priority. Although small patches contain no unique species they preserve landscape processes, have conservation value, and require protection. Conservation principles derived from recently created Amazonian fragments and that emphasize edge-effects, require critical evaluation for application to old Afromontane patches. Nomenclature: Arnold & de Wet (1993).

Aim: Geographical, climatic and soil factors are major drivers of plant beta diversity, but their importance for dryland plant communities is poorly known. The aim of this study was to: (1) characterize patterns of beta diversity in global drylands; (2) detect common environmental drivers of beta diversity; and (3) test for thresholds in environmental conditions driving potential shifts in plant species composition. Location: Global. Methods: Beta diversity was quantified in 224 dryland plant communities from 22 geographical regions on all continents except Antarctica using four complementary measures: the percentage of singletons (species occurring at only one site); Whittaker's beta diversity, β(W); a directional beta diversity metric based on the correlation in species occurrences among spatially contiguous sites, β(R²); and a multivariate abundance-based metric, β(MV). We used linear modelling to quantify the relationships between these metrics of beta diversity and geographical, climatic and soil variables. Results: Soil fertility and variability in temperature and rainfall, and to a lesser extent latitude, were the most important environmental predictors of beta diversity. Metrics related to species identity [percentage of singletons and β (W)] were most sensitive to soil fertility, whereas those metrics related to environmental gradients and abundance [(β(R²) and β(MV)] were more associated with climate variability. Interactions among soil variables, climatic factors and plant cover were not important determinants of beta diversity. Sites receiving less than 178 mm of annual rainfall differed sharply in species composition from more mesic sites (> 200 mm). Main conclusions: Soil fertility and variability in temperature and rainfall are the most important environmental predictors of variation in plant beta diversity in global drylands. Our results suggest that those sites annually receiving c. 178 mm of rainfall will be especially sensitive to future climate changes. These findings may help to define appropriate conservation strategies for mitigating effects of climate change on dryland vegetation.

Aim: We examined the effects of space, climate, phylogeny and species traits on module composition in a cross-biomes plant–hummingbird network. Location: Brazil, except Amazonian region. Methods: We compiled 31 local binary plant–hummingbird networks, combining them into one cross-biomes metanetwork. We conducted a modularity analysis and tested the relationship between species' module membership with traits, geographical location, climatic conditions and range sizes, employing random forest models. We fitted reduced models containing groups of related variables (climatic, spatial, phylogenetic, traits) and combinations of groups to partition the variance explained by these sets into unique and shared components. Results: The Brazilian cross-biomes network was composed of 479 plant and 42 hummingbird species, and showed significant modularity. The resulting six modules conformed well to vegetation domains. Only plant traits, not hummingbird traits, differed between modules, notably plants' growth form, corolla length, flower shape and colour. Some modules included plant species with very restricted distributions, whereas others encompassed more widespread ones. Widespread hummingbirds were the most connected, both within and between modules, whereas widespread plants were the most connected between modules. Among traits, only nectar concentration had a weak effect on among-module connectivity. Main conclusions: Climate and spatial filters were the main determinants of module composition for hummingbirds and plants, potentially related to resource seasonality, especially for hummingbirds. Historical dispersal-linked contingency, or environmental variations not accounted for by the explanatory factors here evaluated, could also contribute to the spatial component. Phylogeny and morphological traits had no unique effects on the assignment of species to modules. Widespread species showed higher within- and/or among-module connectivity, indicating their key role connecting biomes, and, in the case of hummingbirds, communities within biomes. Our results indicate that biogeography and climate not only determine the variation of modularity in local plant–animal networks, as previously shown, but also affect the cross-biomes network structure.

We present a framework to measure the strength of environmental filtering and disequilibrium of the species composition of a local community across time, relative to past, current, and future climates. We demonstrate the framework by measuring the impact of climate change on New World forests, integrating data for climate niches of more than 14 000 species, community composition of 471 New World forest plots, and observed climate across the most recent glacial–interglacial interval. We show that a majority of communities have species compositions that are strongly filtered and are more in equilibrium with current climate than random samples from the regional pool. Variation in the level of current community disequilibrium can be predicted from Last Glacial Maximum climate and will increase with near‐future climate change.

Aim: Despite several recent efforts to map plant traits and to identify their climatic drivers, there are still major gaps. Global trait patterns for major functional groups, in particular, the differences between woody and herbaceous plants, have yet to be identified. Here, we take advantage of big data efforts to compile plant species occurrence and trait data to analyse the spatial patterns of assemblage means and variances of key plant traits. We tested whether these patterns and their climatic drivers are similar for woody and herbaceous plants. Location: New World (North and South America). Methods: Using the largest currently available database of plant occurrences, we provide maps of 200 × 200 km grid-cell trait means and variances for both woody and herbaceous species and identify environmental drivers related to these patterns. We focus on six plant traits: maximum plant height, specific leaf area, seed mass, wood density, leaf nitrogen concentration and leaf phosphorus concentration. Results: For woody assemblages, we found a strong climate signal for both means and variances of most of the studied traits, consistent with strong environmental filtering. In contrast, for herbaceous assemblages, spatial patterns of trait means and variances were more variable, the climate signal on trait means was often different and weaker. Main conclusion: Trait variations for woody versus herbaceous assemblages appear to reflect alternative strategies and differing environmental constraints. Given that most large-scale trait studies are based on woody species, the strikingly different biogeographic patterns of herbaceous traits suggest that a more synthetic framework is needed that addresses how suites of traits within and across broad functional groups respond to climate.

Climate warming is contributing to increases in wildfire activity throughout the western United States, leading to potentially long-lasting shifts in vegetation. The response of forest ecosystems to wildfire is thus a crucial indicator of future vegetation trajectories, and these responses are contingent upon factors such as seed availability, interannual climate variability, average climate, and other components of the physical environment. To better understand variation in resilience to wildfire across vulnerable dry forests, we surveyed conifer seedling densities in 15 recent (1988–2010) wildfires and characterized temporal variation in seed cone production and seedling establishment. We then predicted postfire seedling densities at a 30-m resolution within each fire perimeter using downscaled climate data, monthly water balance models, and maps of surviving forest cover. Widespread ponderosa pine (Pinus ponderosa) seed cone production occurred at least twice following each fire surveyed, and pulses of conifer seedling establishment coincided with years of above-average moisture availability. Ponderosa pine and Douglas-fir (Pseudotsuga menziesii) seedling densities were higher on more mesic sites and adjacent to surviving trees, though there were also important interspecific differences, likely attributable to drought and shade tolerance. We estimated that postfire seedling densities in 42% (for ponderosa pine) and 69% (for Douglas-fir) of the total burned area were below the lowest reported historical tree densities in these forests. Spatial models demonstrated that an absence of mature conifers (particularly in the interior of large, high-severity patches) limited seedling densities in many areas, but 30-yr average actual evapotranspiration and climatic water deficit limited densities on marginal sites. A better understanding of the limitations to postfire forest recovery will refine models of vegetation dynamics and will help to improve strategies of adaptation to a warming climate and shifting fire activity.

Aim Temperature is one of the main drivers shaping species diversity and assembly processes. Yet, site‐specific effects of the local microclimate on species and trait compositions of insect communities have rarely been assessed along macroclimatic temperature clines. Location Bavarian Alps, Germany. Methods Bayesian joint species distribution models were applied to investigate how ecological and morphological traits drive variation in the climatic niches of 32 Orthoptera species on 93 grassland sites with contrasting microclimatic conditions along a steep elevational macroclimatic gradient in an Alpine region in Central Europe. Results Species richness and abundance decreased along the elevational macroclimatic gradient, and both benefitted from warm microclimate. Interactive effects of elevation and microclimate on the abundance were, however, species‐specific, and partly mediated by traits: Warm microclimatic conditions facilitated the occurrence of demanding xerophilic and late‐hatching species, resulting in marked community dissimilarities at mid‐elevations where colder sites harboured only a subset of the species. The latter mainly occurred at low elevations together with long‐winged species. Abundance peaks of non‐xerophilic species were further upslope when microclimate was warm. Intraspecifically, the body sizes and wing lengths of the larger females, but not the males, decreased with elevation akin the community mean, and brown colour morphs were more frequent at sites with warm microclimate. Main Conclusions Our nuanced results reveal that trait‐dependent responses of species to microclimate play a key role in the assembly and structuring of insect communities along macroclimatic gradients. Since microclimate preferences changed with elevation, we conclude that species temperature niches are narrower than the elevational range suggests and both macro‐ and microclimatic conditions must be considered when predicting species responses to climate change. Microclimatic contrasts among sites at similar elevations enhanced species turnover mediated by moisture preferences and phenology, highlighting the importance of mountains for conservation as climatic refugia where species with diverging niches can persist in proximity.