There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
Evidence concerning mechanisms hypothesized to explain species coexistence in hyper-diverse
communities is reviewed for tropical forest plants. Three hypotheses receive strong
support. Niche differences are evident from non-random spatial distributions along
micro-topographic gradients and from a survivorship-growth tradeoff during regeneration.
Host-specific pests reduce recruitment near reproductive adults (the Janzen-Connell
effect), and, negative density dependence occurs over larger spatial scales among
the more abundant species and may regulate their populations. A fourth hypothesis,
that suppressed understory plants rarely come into competition with one another, has
not been considered before and has profound implications for species coexistence.
These hypotheses are mutually compatible. Infrequent competition among suppressed
understory plants, niche differences, and Janzen-Connell effects may facilitate the
coexistence of the many rare plant species found in tropical forests while negative
density dependence regulates the few most successful and abundant species.