Region effects influence local tree species diversity

Abstract

Global patterns of biodiversity reflect both regional and local processes, but the relative importance of local ecological limits to species coexistence, as influenced by the physical environment, in contrast to regional processes including species production, dispersal, and extinction, is poorly understood. Failure to distinguish regional influences from local effects has been due, in part, to sampling limitations at small scales, environmental heterogeneity within local or regional samples, and incomplete geographic sampling of species. Here, we use a global dataset comprising 47 forest plots to demonstrate significant region effects on diversity, beyond the influence of local climate, which together explain more than 92% of the global variation in local forest tree species richness. Significant region effects imply that large-scale processes shaping the regional diversity of forest trees exert influence down to the local scale, where they interact with local processes to determine the number of coexisting species.

Drivers of elevational richness peaks, evaluated for trees in the east Himalaya

“…Previous studies along east Himalayan elevational gradients have specifically invoked climate, both precipitation and temperature (Acharya et al. ) and precipitation and temperature seasonality (Li and Feng ), as drivers of plant richness patterns, in accordance with both our inferences and global analyses of plants (Kreft and Jetz ) and trees in particular (Ricklefs and He ).…”

Elevational gradients in plant defences and insect herbivory: recent advances in the field and prospects for future research

“…For instance, the geological age of a mountain range influences communities along elevational gradients as older mountains allow for more species colonization and diversification (Schemske and Mittelbach 2017). In addition, local diversity at different elevations is shaped by the regional species pool and the species available to populate a given mountain range (Ricklefs and He 2016). Likewise, some mountain ranges have served as species refugia during glaciation periods (Schönswetter et al 2005), and such historical contingencies may shape variation in biotic communities among mountain ranges.…”

Plant species richness across the Himalaya driven by evolutionary history and current climate

“…We used structural equation models (Kline 2015) to disentangle effects of current climate and evolutionary history on patterns of species richness. Kluge et al (2017) suggested a quadratic relationship with temperature might explain plant species richness patterns across an elevational gradient in Bhutan, but the mechanism by which this might arise is unclear, and in general, warm wet areas have more species globally Jetz 2007, Ricklefs andHe 2016). We take this approach because a priori hypotheses for the effects of climate, history, and competitors all assume monotonic increases or decreases with each variable, at least over the range present in our dataset (Rana et al 2019).…”

“…Regions experiencing low extinction, high speciation, and high immigration are expected to have more species than those with the opposite processes. In plants, evidence for contributions from non-equilibrium historical processes to local diversity is strong Ricklefs 2000, Ricklefs andHe 2016). In contrast to historical effects, the number of species present in a location may be largely a function of present-day climate (Currie et al 2004), irrespective of past history.…”