The current hybridization between the endemic Morus boninensis Koidz. and the invasive Morus australis Poir. in the Ogasawara Islands

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  • 小笠原諸島における固有種オガサワラグワと侵略的外来種シマグワとの交雑の現状

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Abstract

Impacts of invasive alien plant species on its closely related endemic ones in oceanic islands are often problematic because hybridization may occur between them. This study focused on endemic Morus boninensis (tetraploid of 2n=56) and its related invasive species M. australis (diploid of 2n=28) in the Ogasawara Islands. Aim of this study is to estimate proportion of the hybrids between the two species in wild seedling of native habitats of M. boninensis and to evaluate the current genetic diversity of M. boninensis. Observations and collections of plant samples were conducted in two wild seedling populations, two mature tree populations of M. boninensis and 12 populations of M. australis in the Ogasawara Islands. The 14 microsatellite markers were used for population genetic analyses. Based on the results of UPGMA analysis, the Principal Coordinate Analysis (PCoA), and the Bayesian Clustering, clear genetic differentiation was detected between the two species in the Ogasawara Islands. Gene flows between them unlikely or rarely occur maybe due to the difference in ploidy level. Hybrids were not found in the seedling populations, either. Limited effects of M. australis to the endangered M. boninensis through hybridization were detected in this study. It was also shown that M. boninensis still maintains high genetic diversity (HE = 0.53; AR = 3.27) despite that it is endangered species. It may be able to survive if the number of the individuals of the endangered species could be increased.

Journal

  • Ogasawara research

    Ogasawara research 48 217-235, 2022-03

    東京都立大学小笠原研究委員会

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