A Global Evaluation of Metabolic Theory as an Explanation for Terrestrial Species Richness Gradients

Abstract

Abstract. We compiled 46 broadscale data sets of species richness for a wide range of terrestrial plant, invertebrate, and ectothermic vertebrate groups in all parts of the world to test the ability of metabolic theory to account for observed diversity gradients. The theory makes two related predictions: (1) ln-transformed richness is linearly associated with a linear, inverse transformation of annual temperature, and (2) the slope of the relationship is near À0.65. Of the 46 data sets, 14 had no significant relationship; of the remaining 32, nine were linear, meeting prediction 1. Model I (ordinary least squares, OLS) and model II (reduced major axis, RMA) regressions then tested the linear slopes against prediction 2. In the 23 data sets having nonlinear relationships between richness and temperature, split-line regression divided the data into linear components, and regressions were done on each component to test prediction 2 for subsets of the data. Of the 46 data sets analyzed in their entirety using OLS regression, one was consistent with metabolic theory (meeting both predictions), and one was possibly consistent. Using RMA regression, no data sets were consistent. Of 67 analyses of prediction 2 using OLS regression on all linear data sets and subsets, two were consistent with the prediction, and four were possibly consistent. Using RMA regression, one was consistent (albeit weakly), and four were possibly consistent. We also found that the relationship between richness and temperature is both taxonomically and geographically conditional, and there is no evidence for a universal response of diversity to temperature. Meta-analyses confirmed significant heterogeneity in slopes among data sets, and the combined slopes across studies were significantly lower than the range of slopes predicted by metabolic theory based on both OLS and RMA regressions. We conclude that metabolic theory, as currently formulated, is a poor predictor of observed diversity gradients in most terrestrial systems.

Macrofungal diversity in Colombian Amazon forests varies with regions and regimes of disturbance

“…It is unlikely that a single model explains the patterns that influence species diversity for any group of organisms in different ecosystems. Many hypotheses resulting from meta studies explain the distribution and patterns of species richness of birds (Davies et al 2007;Rahbek et al 2007), vascular plants (Kreft and Jetz 2007), and plants and animals (Hawkins et al 2007;Whittaker et al 2007), but none of these studies took fungi into account. The number of macrofungal species on its own is not a good parameter to estimate the ecological quality of mycobiota occurring in Amazon forests.…”

Evolving ecological networks and the emergence of biodiversity patterns across temperature gradients

“…In order to quantify temperature-diversity patterns through time, we used break-point regression which fits linear functions to either side of an inflection point [40] (see also Hawkins et al [5] for a conceptually similar approach). For each point in time, a ratio of the two linear slopes was calculated with the shallowest slope in the numerator, constraining the ratio between þ1 and 21.…”

Testing Metabolic Theories

“…The debate in the literature about metabolic theory has mostly focused on the validity of the assumptions and predictive capacity of the higher profile but more recently formulated WBE theory (e.g., Kozłowski and Konarzewski 2004;Algar et al 2007;Hawkins et al 2007;Apol et al 2008;Martínez del Rio 2008;Isaac and Carbone 2010). Surprisingly, the DEB theory has been almost completely overlooked by the proponents and commentators of the WBE-style metabolic theory despite its existence in the literature since the 1980s.…”