A skewed picture of functional diversity in global drylands

Recently, Gross et al. (Nature 632, 808-814) found that plant phenotypic diversity dramatically increases with aridity globally, challenging conventional environmental filtering theories. However, some methodological choices by Gross et al. might overestimate the effect of aridity on phenotypic diversity: (i) We detected a skewed distribution of sampling sites towards the arid end of the analyzed gradient; (ii) We posited that fine-tuning of some statistical parameters might further challenge their estimates. We reanalyzed Gross et al. data accounting for these effects and found a substantially reduced change of phenotypic diversity with increasing aridity. Gross et al. surely represents a cornerstone for future research on trait diversity in a drier world, but their interpretations need to be considered alongside our findings. Importantly, the points raised by our reanalysis provide general guidelines for future research on plant phenotypic diversity changes along environmental gradients.