Global Patterns of Tree Species Richness in Moist Forests: Another Look

After examining some perceived inconsistencies in the relationship between species richness and energy, Latham and Ricklefs rejected the Energy Diversity Theory in favour of historical explanations of the geographical patterns of tree species richness. We have re-examined Latham and Ricklefs's data, both by itself and pooled with Currie and Paquin's data. We find that Latham and Ricklefs's data are, in fact, consistent with the richness-energy hypothesis. Because of strong collinearity between annual evapotranspiration and region in their particular data sets, the data cannot be used to distinguish between the hypotheses that contemporary climate, versus some other interregional difference, is responsible for observed species richness patterns. Finally, there is no particular reason to attribute differences among regions to historical factors rather than to contemporary ones.