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Science 27 January 2006:
Vol. 311. no. 5760, pp. 527 - 531
DOI: 10.1126/science.1117715
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Reports

Nonrandom Processes Maintain Diversity in Tropical Forests

Christopher Wills,1* Kyle E. Harms,2,3 Richard Condit,3 David King,4 Jill Thompson,5 Fangliang He,6 Helene C. Muller-Landau,7 Peter Ashton,4 Elizabeth Losos,8 Liza Comita,9 Stephen Hubbell,9 James LaFrankie,10 Sarayudh Bunyavejchewin,11 H. S. Dattaraja,12 Stuart Davies,4 Shameema Esufali,13 Robin Foster,14 Nimal Gunatilleke,13 Savitri Gunatilleke,13 Pamela Hall,15 Akira Itoh,16 Robert John,17 Somboon Kiratiprayoon,18 Suzanne Loo de Lao,3 Marie Massa,8 Cheryl Nath,12 Md. Nur Supardi Noor,19 Abdul Rahman Kassim,19 Raman Sukumar,12 Hebbalalu Satyanarayana Suresh,12 I-Fang Sun,20 Sylvester Tan,21 Takuo Yamakura,16 Jess Zimmerman5

An ecological community's species diversity tends to erode through time as a result of stochastic extinction, competitive exclusion, and unstable host-enemy dynamics. This erosion of diversity can be prevented over the short term if recruits are highly diverse as a result of preferential recruitment of rare species or, alternatively, if rare species survive preferentially, which increases diversity as the ages of the individuals increase. Here, we present census data from seven New and Old World tropical forest dynamics plots that all show the latter pattern. Within local areas, the trees that survived were as a group more diverse than those that were recruited or those that died. The larger (and therefore on average older) survivors were more diverse within local areas than the smaller survivors. When species were rare in a local area, they had a higher survival rate than when they were common, resulting in enrichment for rare species and increasing diversity with age and size class in these complex ecosystems.

1 Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093–0116, USA.
2 Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
3 Smithsonian Tropical Research Institute, Unit 0948, APO AA 34002-0948, Panama.
4 Center for Tropical Forest Science, Arnold Arboretum Asia Program, Harvard University, Herbaria, 22 Divinity Avenue, Cambridge, MA 02138, USA.
5 Institute for Tropical Ecosystem Studies, University of Puerto Rico, Post Office Box 21910, San Juan, PR 00931–1910, USA.
6 Department of Renewable Resources, University of Alberta, Edmonton AB, T6G 2H1, Canada.
7 Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN 55108, USA.
8 Center for Tropical Forest Science, Smithsonian Tropical Research Institute, 1100 Jefferson Drive, Suite 3123, Washington, DC 20560–0705, USA.
9 Department of Plant Sciences, University of Georgia, 2502 Miller Plant Sciences Building, Athens, GA 30602, USA.
10 Center for Tropical Forest Science, Arnold Arboretum Asia Program, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, 637616, Singapore.
11 Thai National Park Wildlife and Plant Conservation Department, Silviculture Research, 61 Phaholyothin Road, Chatuchak Bangkok 10900, Thailand.
12 Center for Ecological Sciences, Indian Institute of Science, Bangalore 560012, India.
13 Department of Botany, Faculty of Science, University of Peradeniya, Peradeniya 20400, Sri Lanka.
14 Botany Department, The Field Museum, Roosevelt Road at Lake Shore Drive, Chicago, IL 60605–2496, USA.
15 Department of Biology, Florida State University, 5051 Quail Valley Road, Tallahassee, FL 32309, USA.
16 Plant Ecology Lab, Faculty of Science, Osaka City University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558, Japan.
17 Department of Plant Biology, University of Illinois, 505 South Goodwin Avenue, 265 Morrill Hall, Urbana, IL 61801, USA.
18 Faculty of Science and Technology, Thammasat University (Rangsit), Klongluang, Patumtani, 12121, Thailand.
19 Forest Environment Division, Forest Research Institute Malaysia, Kepong, Kuala Lumpur 52109, Malaysia.
20 Center for Tropical Ecology and Biodiversity, Tunghai University, 407 Taipei, Taiwan.
21 Forest Research Center, Sarawak Forest Department, Km10 Jalun Datak Amar Kalong Ningkan, 93250 Kuching, Sarawak, Malaysia.

* To whom correspondence should be addressed. E-mail: cwills{at}ucsd.edu

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