Global variation in elevational diversity patterns

Abstract

While horizontal gradients of biodiversity have been examined extensively in the past, vertical diversity gradients (elevation, water depth) are attracting increasing attention. We compiled data from 443 elevational gradients involving diverse organisms worldwide to investigate how elevational diversity patterns may vary between the Northern and Southern hemispheres and across latitudes. Our results show that most elevational diversity curves are positively skewed (maximum diversity below the middle of the gradient) and the elevation of the peak in diversity increases with the elevation of lower sampling limits and to a lesser extent with upper limit. Mountains with greater elevational extents, and taxonomic groups that are more inclusive, show proportionally more unimodal patterns whereas other ranges and taxa show highly variable gradients. The two hemispheres share some interesting similarities but also remarkable differences, likely reflecting differences in landmass and mountain configurations. Different taxonomic groups exhibit diversity peaks at different elevations, probably reflecting both physical and physiological constraints. Montane regions harbor more than half of the world's biodiversity hotspots and recent research on biodiversity patterns has been notable for an increase in research on elevational patterns on mountains 1 . Mountains provide unique opportunities as 'natural experiments' for testing ecological theories and in particular for studying the effects of climate change because they present gradients in key abiotic features such as temperature and available moisture. Recent efforts have generated interesting and sometimes conflicting results, and debates on the generality of the frequently observed unimodal (''hump-shaped'' 2 ) curves and the underlying mechanisms have not been fully resolved. Indeed, despite increased research in this area in recent years, employing markedly improved techniques and greater sampling intensity, much inconsistency and debate remains both in pattern description and interpretation. For example, surprisingly little effort has targeted how elevational diversity patterns might vary in the Northern and Southern hemispheres and across latitudinal zones [3][4][5][6][7] . To tackle these problems, detailed comparisons are needed over distinct (replicate) elevational gradients across the globe.The upper elevational limit for phanerogams varies as a function of latitude and generally reflects limits to physiologic tolerance 1 . Moreover, similar elevational ranges in different regions are likely to exhibit different underlying gradients 8 , reflecting regional climate and geography; cold-temperate mountains lack the warm climate characteristic of lower elevations at lower latitudes, and temperatures at a tropical treeline might reflect those at the base of cold-temperate mountains. Additionally, the effect of aspect is greatly reduced on tropical mountains relative to temperate ones. As a result of these latitudinal differences, structurally identical mountains locate...

Diversity and distribution of autotrophic microbial community along environmental gradients in grassland soils on the Tibetan Plateau

“…Elevation usually encompasses primary change in climatic conditions (temperature and precipitation) and consequently results in a corresponding change in vegetation and soil physicochemical factors (Guo et al 2013b;Nogues-Bravo et al 2008;Wang et al 2013). At this study site of the Tibetan Plateau, higher elevation exhibited higher precipitation and lower temperature, which consequently induced higher plant growth (Wang et al 2013), soil water content and nutrients (TOC and NH 4 + ), but lower soil pH (Table S1).…”

Tree species composition and richness along altitudinal gradients as a tool for conservation decisions: the case of Atlantic semideciduous forest

“…The effect of altitude on the variation of taxa composition, floristic diversity and structure of forest formations has been widely demonstrated (Gaston 2000;Grytnes and Beaman 2006;Guo et al 2013;Sanchez et al 2013). The observed changes in the vegetation are influenced by a number of abiotic factors that accompany the altitudinal gradient, such as decreasing atmospheric pressure, reduced temperature, and increased solar radiation (Körner 2007;Barry 2008;McCain and Grytnes 2010).…”

Variation in freshwater fish assemblages along a regional elevation gradient in the northern Andes, Colombia

“…The main recent reviews of the origin and maintenance of diversity in elevation gradients either made no mention of studies on freshwater fishes (see Sanders and Rahbek 2011), or it was the least represented taxonomic group (see Guo et al. 2013; Graham et al. 2014).…”