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Habitat divergence in sympatric Fagaceae tree species of a tropical montane forest in northern Thailand

Published online by Cambridge University Press:  16 August 2007

Hideyuki Noguchi
Affiliation:
Graduate School of Science, Osaka City University, Sugimoto 3-3-138, Sumiyoshi, Osaka 558–8585, Japan
Akira Itoh
Affiliation:
Graduate School of Science, Osaka City University, Sugimoto 3-3-138, Sumiyoshi, Osaka 558–8585, Japan
Takashi Mizuno
Affiliation:
Graduate School of Science, Osaka City University, Sugimoto 3-3-138, Sumiyoshi, Osaka 558–8585, Japan
Kriangsak Sri-ngernyuang
Affiliation:
Faculty of Architecture and Environmental Design, Maejo University, Chiang Mai 50290, Thailand
Mamoru Kanzaki
Affiliation:
Graduate School of Agriculture, Kyoto University, Kyoto 606–8502, Japan
Sakhan Teejuntuk
Affiliation:
Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
Witchaphart Sungpalee
Affiliation:
Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
Masatoshi Hara
Affiliation:
Natural History Museum and Institute, Chiba, Chiba 260–8682, Japan
Tatsuhiro Ohkubo
Affiliation:
Faculty of Agriculture, Utsunomiya University, Utsunomiya 321-8505, Japan
Pongsak Sahunalu
Affiliation:
Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
Pricha Dhanmmanonda
Affiliation:
Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
Takuo Yamakura
Affiliation:
Graduate School of Science, Osaka City University, Sugimoto 3-3-138, Sumiyoshi, Osaka 558–8585, Japan

Abstract

Spatial distributions of many tropical trees are skewed to specific habitats, i.e. habitat specialization. However, habitats of specialist species must be divergent, i.e. habitat divergence, to coexist in a local community. When a pair of species specialize in the same habitat, i.e. habitat convergence, they could not coexist by way of habitat specialization. Thus, analyses of habitat divergence, in addition to habitat specialization, are necessary to discuss coexistence mechanisms of sympatric species. In this study, the habitat specialization and habitat divergence along topographic gradients of eight sympatric tree species of the Fagaceae were studied in a 15-ha study plot in a tropical lower montane forest in northern Thailand. A statistical test with torus shift randomizations for 9673 trees of Fagaceae revealed significantly biased distributions for all of the species, for at least one of the four topographic variables used: elevation, slope inclination, aspect and convexity. Slope convexity was the most critical topographic variable, along which all but one species had significantly skewed distributions. Out of 112 possible combinations of species pairs and topographic variables, 18 (16%) and two pairs (1.8%) showed significant habitat divergence and habitat convergence, respectively. The observed habitat divergence alone could not completely explain the coexistence of the eight species. There was a gradation in the habitat position of each species, with relatively large overlaps between species distributed in similar habitats, and small overlaps between species associated with contrasting habitats, respectively. The gradual changes in the habitats of the species suggested that dividing the species into a small number of distinct habitat groups, such as ridge and valley specialists, would not be straightforward.

Type
Research Article
Copyright
2007 Cambridge University Press

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