Species assemble into communities through ecological and evolutionary processes. Phylogenetic niche conservatism—the tendency of species to retain ancestral ecological distributions—is thought to influence which species from a regional species pool can persist in a particular environment. We analyzed data for seed plants in China to test hypotheses about the distribution of species within regional floras. Of 16 environmental variables, actual evapotranspiration, minimum temperature of the coldest month, and annual precipitation most strongly influenced regional species richness, phylogenetic dispersion, and phylogenetic diversity for both gymnosperms (cone-bearing plants) and angiosperms (flowering plants). For most evolutionary clades at, and above, the family level, the relationships between metrics of phylogenetic dispersion (i.e., average phylogenetic distance among species), or phylogenetic diversity, and the 3 environmental variables were consistent with the tropical niche conservatism hypothesis, which predicts closer phylogenetic relatedness and reduced phylogenetic diversity with increasing environmental stress. The slopes of the relationships between phylogenetic relatedness and the 3 environmental drivers identified in this analysis were steeper for primarily tropical clades, implying greater niche conservatism, than for primarily temperate clades. These observations suggest that the distributions of seed plants across large-scale environmental gradients in China are constrained by conserved adaptations to the physical environment, i.e., phylogenetic niche conservatism.

Aim Ecologists have generally agreed that β‐diversity is driven at least in part by ecological processes and mechanisms of community assembly and is a key determinant of global patterns of species richness. This idea has been challenged by a recent study based on an individual‐based null model approach, which aims to account for the species pool. The goal of the present study is twofold: (1) to analyse data sets from different parts of the world to determine whether there are significant latitude–β‐diversity gradients after accounting for the species pool, and (2) to evaluate the validity of the null model. Location Global. Methods A total of 257 forest plots, each being 0.1 ha in size and having 10 0.01‐ha subplots, were used. We conducted four sets of analyses. A modified version of Whittaker's β‐diversity index was used to quantify β‐diversity for each forest plot. A randomization procedure was used to determine expected β‐diversity. Results The number of individuals per species, which characterizes species abundance distribution, alone explains 56.8–84.2% of the variation in observed β‐diversity. Species pool (γ‐diversity) explained only an additional 2.6–15.2% of the variation in observed β‐diversity. Latitude explains 18.6% of the variation in raw β deviation in Gentry's global data set, and explains 11.0–11.6% of the variation in standardized β deviation in the global and three regional analyses. Latitude explains 33.2–46.2% of the variation in the number of individuals per species. Main conclusions Species abundance distribution, rather than species pool size, plays a key role in driving latitude–β‐diversity gradients for β‐diversity in local forest communities. The individual‐based null model is not a valid null model for investigating β‐diversity gradients driven by mechanisms of local community assembly because the null model incorporates species abundance distributions, which are driven by mechanisms of local community assembly and in turn generate β‐diversity gradients.

Aim Endemic species are hypothesized to particularly occur in areas with relatively stable climates during the Quaternary glacial-interglacial oscillations (orbitally forced species' range dynamics hypothesis). This hypothesis has received support in global studies and studies from regions highly affected by glaciations. Here, we test its applicability to Chinese endemic species, thereby testing it in a region that was relatively mildly affected by glaciations.Location China. MethodsWe tested for associations between endemic species richness and Quaternary climate change, current climate and topography. Changes in mean annual temperature (MAT) and annual precipitation (MAP) between the Last Glacial Maximum and present were used to describe Quaternary climate change. We used simultaneous autoregressive (SAR) models to account for spatial autocorrelation in predictors, and Random Forest modelling to deal with non-linear relationships and better handle multicollinearity among predictor variables. To get a deeper understanding of the mechanisms involved we also performed analyses based on growth-form (woody versus herbaceous plants) and species age (palaeo-and neoendemics).Journal of Biogeography (J. Biogeogr.) (2016) 43, 145-154 SUPPORTING INFORMATIONAdditional Supporting Information may be found in the online version of this article:Appendix S1 Results of SAR models of endemic species richness against variables at 4-cell scale after removing the larger counties, and the two islands. Appendix S2 Correlations of all variables and result of single factor SAR models at 4-cell scale. Appendix S3 Results based on the endemism definition at 16-cell scale and results on non-endemic species richness at 4-cell scale.