Comparison of contemporary mating patterns in continuous and fragmented Eucalyptus globulus native forests

Authors

  • MAKIKO MIMURA,

    1. Graduate School of Life and Environmental Sciences, University of Tsukuba, Tenoudai 1-1-1,Tsukuba, Japan
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    • Present address: Environmental and Information Sciences, Yokohama National University, Tokiwadai 79-7, Hodogaya,Yokohama, 240-8501, Japan.

  • ROBERT C. BARBOUR,

    1. School of Plant Science and CRC for Forestry, University of Tasmania, Private Bag 55, Hobart, Australia
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  • BRAD M. POTTS,

    1. School of Plant Science and CRC for Forestry, University of Tasmania, Private Bag 55, Hobart, Australia
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  • RENÉ E. VAILLANCOURT,

    1. School of Plant Science and CRC for Forestry, University of Tasmania, Private Bag 55, Hobart, Australia
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  • KAZUO N. WATANABE

    1. Graduate School of Life and Environmental Sciences, University of Tsukuba, Tenoudai 1-1-1,Tsukuba, Japan
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  • M.M. investigates factors influencing quantitative and genetic divergences among populations, including gene flow. K.N.W.'s research focuses on ecological biosafety and developing frameworks to control risks of gene flow from transgenic crop and trees. The Tasmanian researchers (RCB, BMP and REV) specialize in the quantitative and molecular genetics of eucalypts and Eucalyptus globulus, is their model species. They are interested in pollen-mediated gene flow to better understand micro-evolutionary processes as well as to assist in the development of strategies to assess and manage the risk of gene flow from planted to native eucalypts in Australia.

Makiko Mimura, Fax: +81 45 339 4375; E-mail: mimura@ynu.ac.jp

Abstract

While habitat fragmentation is a central issue in forest conservation studies in the face of broad-scale anthropogenic changes to the environment, its effects on contemporary mating patterns remain controversial. This is partly because of the inherent variation in mating patterns which may exist within species and the fact that few studies have replication at the landscape level. To study the effect of forest fragmentation on contemporary mating patterns, including effective pollen dispersal, we compared four native populations of the Australian forest tree, Eucalyptus globulus. We used six microsatellite markers to genotype 1289 open-pollinated offspring from paired fragmented and continuous populations on the island of Tasmania and in Victoria on mainland Australia. The mating patterns in the two continuous populations were similar, despite large differences in population density. In contrast, the two fragmented populations were variable and idiosyncratic in their mating patterns, particularly in their pollen dispersal kernels. The continuous populations showed relatively high outcrossing rates (86–89%) and low correlated paternity (0.03–0.06) compared with the fragmented populations (65–79% and 0.12–0.20 respectively). A greater proportion of trees contributed to reproduction in the fragmented (de/d≥ 0.5) compared with the continuous populations (de/d = 0.03–0.04). Despite significant inbreeding in the offspring of the fragmented populations, there was little evidence of loss of genetic diversity. It is argued that enhanced medium- and long-distance dispersal in fragmented landscapes may act to partly buffer the remnant populations from the negative effects of inbreeding and drift.

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