Diversity in Tropical Forests

Abstract

In her article “Rare tree species thrive in local neighborhoods” (News of the Week, 27 Jan., p. 452) discussing a study by C. Wills et al. (“Nonrandom processes maintain diversity in tropical forests,” Reports, 27 Jan., p. [527][1]), E. Pennisi states that “Biodiversity may be threatened worldwide, but small pockets of tropical-forest trees are surprisingly becoming more diverse over time.” However, the key implication of Wills et al. 's study is that, in several tropical forests on two different continents, strong density-and frequency-dependent mortality tends to favor rare over common tree species locally (at a scale of tens to hundreds of square meters), and that this is a key process that helps to maintain (but not increase) tree diversity at a forest-wide scale. Hence, Wills et al. have helped to reveal the mechanisms by which tropical forests maintain their extraordinary biological diversity, but there is nothing in their study to suggest that the number of species in these forests is somehow increasing. [1]: /lookup/doi/10.1126/science.1117715