Elevational gradients in diversity at two contrasting spatial scales.

<p>Small (among 0.01-ha subplots within a 0.1-ha plot; top row) and large (among 0.1-ha plots within an elevational band; bottom row). A) and D) Regional (γ-) and local (α-) diversity. B) and E) Observed β-diversity and mean null β-diversity. C) and F) β-deviations (standardized effect sizes of β-diversity). Null β-diversity and β-deviations were calculated based on two null models, one that randomizes the regional species abundance distribution (r-SAD) and one that fixes it to be identical to the one observed in the empirical data (f-SAD; see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121458#sec002" target="_blank">Methods</a>). Diversity was partitioned following Jost [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121458#pone.0121458.ref043" target="_blank">43</a>] and by weighting each species proportionally by its abundance (i.e. diversity of order 1). All relationships were statistically significant (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121458#pone.0121458.t001" target="_blank">Table 1</a>).</p

Comparisons of the strength and shape of elevational gradients between scales and between observed β-diversity and β-deviations.

<p>β-deviations were calculated using the random SAD (r-SAD) and fixed SAD (f-SAD) null models (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121458#sec002" target="_blank">Methods</a>). A) Strength of the gradients measured using adjusted R² values (_adj.R²) from cubic regressions between diversity and elevation. Black circles represent original _adj.R² estimates. Grey regions show the distribution of values based on 1,999 bootstrapped regressions. Black lines represent 99% confidence intervals. B) Shape of the gradients measured using standardized regression coefficients. Only the coefficients for elevation (b₁) and elevation squared (b₂) are presented. Other coefficients lead to similar conclusions. Black symbols represent original estimates. Black arrows show the change in coefficients between observed β-diversity and β-deviations at a given spatial scale. Black lines represent 99% data ellipses which define confidence regions. Other symbols show the distribution of values based on bootstrapped regressions.</p

Distributions of 2,668 woody plant species along the elevational gradient.

<p>Each vertical line represents the elevational range of a species in the Madidi region. Ranges are defined as the interval between the lowest and highest elevations at which a species was found within the full network of plots. The horizontal dashed line marks the elevation at which there seems to be a break in the continuous turnover in forest composition along the elevational gradient. Above 3,725 m, forests are composed only of 3 woody plant species: <i>Gynoxys asterotricha</i>, <i>G</i>. <i>compressissima</i> and <i>Polylepis pepei</i>.</p

Variation in the overall magnitude of β-deviations between small and large spatial scales.

<p>β-deviations were calculated using the random SAD (r-SAD) and fixed SAD (f-SAD) null models (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121458#sec002" target="_blank">Methods</a>). The horizontal grey line marks the value of no difference from null model expectations (i.e. β-deviation of zero). β-deviations above the line indicate higher β-diversity than expected by random sampling of individuals from observed species pools. Note that β-deviations are higher at large scales than at small scales (linear mixed-effects model: <i>t</i>₂₇₆ < 38.97; <i>p</i> < 0.001). In addition, mean β-deviations are statistically different from zero for all combinations of spatial scale and null model (one sample t-tests: |<i>t</i>| > 4.77; p < 0.001).</p

Regional network of forest plots sampled as part of The Madidi Project, a floristic inventory of northwestern Bolivia.

<p>The map shows the locations of 440 0.1-ha plots along a 4000-m elevational gradient in the Andes. A) Study region in Bolivia. B) and C) Distribution of plots along the eastern slopes of the Andes (∼250–4,350 m) in and around the multiple protected areas that form part of the Madidi region. Elevation data from WorldClim (<a href="http://www.worldclim.org" target="_blank">www.worldclim.org</a>); country borders from the GADM database (<a href="http://gadm.org" target="_blank">gadm.org</a>).</p