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The distance dependence prediction of the Janzen-Connell hypothesis: a meta-analysis

Authors

  • Laura A. Hyatt,

  • Michael S. Rosenberg,

  • Timothy G. Howard,

  • Gregory Bole,

  • Wei Fang,

  • Jean Anastasia,

  • Kerry Brown,

  • Rebecca Grella,

  • Katharine Hinman,

  • Josepha P. Kurdziel,

  • Jessica Gurevitch


L. A. Hyatt, M. S. Rosenberg, T. G. Howard, G. Bole, W. Fang, J. Anastasia, K. Brown, R. Grella, K. Hinman, J. P.Kurdziel and J. Gurevitch, Dept of Ecology and Evolution, State Univ. of New York, Stony Brook, NY 11794-5245, USA (lhyatt@rider.edu). Present address for LAH: Dept of Biology, Rider Univ., Lawrenceville, NJ 08648, USA. Present address for MSR: Dept of Biology, Arizona State Univ., P.O. Box 871501, Tempe, AZ 85287-1501, USA. Present address for TGH: New York Natural Heritage Program, 625 Broadway, 5th Floor, Albany, NY 12233-4757, USA. Present address for BG: Univ. College of the Fraser Valley, 33844 King Rd, Abbotsford, Brittish Columbia, V2S 7M8 Canada. Present address for JA: Biology Dept, Ammerman Campus, Suffolk Community College, Smithtown Science Building (T-104) 533 College Road, Selden, NY 11784-2899, USA. Present address forRG: Aiza Biby, P.O. Box 701, East Setauket, NY 11733, USA. Present address for KH: Arizona Game and Fish Dept, Nongame Branch, 2221 W. Greenway Road WMNG, Phoenix, AZ 85023-4399, USA. Present address for JPK: Dept of Ecology and Evolutionary Biology, The Univ. of Michigan, Natural Science Building (Kraus), 830 North Univ., Ann Arbor, MI 48109-1048, USA.

Abstract

The Janzen-Connell hypothesis explains the maintenance of tropical diversity through the interacting effects of parent-centered dispersal patterns and distance- and density-dependent propagule survival. These effects were thought to support regular spacing of species within tropical forest, enhancing diversity. One of the predictions of the hypothesis is that seed and seedling survival should improve with increased parental distance. Although there are many independent tests of this hypothesis for individual species, there are few synthetic studies that have brought these data together to test its validity across species. This paper reports the results of a meta-analysis of the effect of distance on enhancing propagule survival, employing an odds-ratio effect size metric. We found no general support for the distance-dependent prediction of the hypothesis, and conclude that further testing to explore this hypothesis as a diversity-maintaining mechanism is unnecessary. However, we did find that distance from parent slightly reduces survivorship in the temperate zone, as contrasted with the tropics, and we saw stronger evidence in support of the hypothesis for seedlings than for seeds. The phenomenon of enhanced propagule survival with distance from the parent may be important for the population biology of particular species, but it is not a general phenomenon across communities, life history stages or life forms.

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