, Volume 130, Issue 1, pp 1-14

Plant diversity in tropical forests: a review of mechanisms of species coexistence

  • Joseph S. WrightAffiliated withSmithsonian Tropical Research Institute, Apartado 2072, Balboa, Ancón, Republic of Panama

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


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.

Alpha diversity Density dependence Disturbance Host-specific pests Janzen-Connell hypothesis