Genetic and reproductive consequences of forest fragmentation for populations of <Emphasis Type="Italic">Magnolia obovata</Emphasis> |
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Authors: | Yuji Isagi Ryunosuke Tateno Yu Matsuki Akira Hirao Sonoko Watanabe Mitsue Shibata |
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Institution: | (1) Graduate School of Agriculture, Kyoto University, Kitashivakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan;(2) Graduate School of Agriculture, Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan;(3) Graduate School for International Development and Cooperation, Hiroshima University, Kagamiyama 1-5-1, Higashi-Hiroshima 739-8529, Japan;(4) Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan;(5) Tohoku Research Center, Forestry and Forest Products Research Institute, Morioka, Iwate 020-0123, Japan |
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Abstract: | In order to evaluate the consequences of forest fragmentation on populations of Magnolia obovata, we compared genetic diversity and reproductive characteristics at two nearby sites, one conserved and one fragmented. The
genetic diversity between adults trees of the different sites was not significantly different. However, saplings in the conserved
site showed a significantly higher genetic diversity than both adult trees in the conserved site and saplings in the fragmented
sites; this was found to be the result of the larger gene flow into the conserved site. The density of the adult trees was
significantly related to all of the reproductive traits analyzed (fertilization of ovules, insect attack to seeds, ovules
that developed into seeds and outcrossing at the stage of seeds) at both sites. At both sites, fertilization of ovules and
insect attack on seeds were positively correlated to adult tree density while outcrossing rate was negatively correlated to
adult tree density. The fertilization of ovules and outcrossing were more dependent on adult tree density in the fragmented
site than in the conserved site. The probability of ovules developing into outcrossed seeds showed a negative correlation
with adult tree density at both sites, indicating the advantage of low density for this species and possibly implying a resilience
to habitat fragmentation. A two-generation-analysis did not identify significant differences between sites in terms of the
structure of the pollen pool and the number of pollen donors. Although fragmentation affected reproductive characteristics,
the effect on seedling establishment and subsequent survival remains to be determined. Proposals for future studies that will
assist in the development of management strategies for forests suffering fragmentation are made. |
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Keywords: | Fecundity Forest fragmentation Fruition Regeneration Pollination |
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