Influence of inbreeding depression on a lake population of Nymphoides peltata after restoration from the soil seed bank
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The negative effects of inbreeding depression on fragmented small populations are likely to be expressed more strongly after restoration efforts if regeneration processes have been highly restricted in degraded habitats. We examined the potential influences of inbreeding depression on a population of Nymphoides peltata (Menyanthaceae) restored from the remnant soil seed bank. A hand-pollination experiment demonstrated self-compatibility of a single remaining homostyle genet and significant inbreeding depression in selfed progeny, especially in parameters related to seedling growth (\(\updelta=0.5\)–0.6 for biomass, and \(\updelta=0.3\)–0.4 for relative growth rate). Our genetic analysis indicated that the presumed number of parents contributing to the current soil seed bank was only 2–8 genets and that a single sib-family dominated at each of three sampling sites. The results also showed that the selfed progeny of the homostyle genet were overwhelmingly dominant at two sites (86.8 and 94.7%). As a result, the growth performance of the seed bank seedlings was significantly reduced, to a level as low as that of the selfed progeny. Active restoration efforts to minimize the negative effects of the genetic bottleneck and continuous monitoring based on genetic and demographic study are recommended.
Key wordsbottleneck inbreeding depression microsatellite offspring fitness restoration soil seed bank
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We thank the Kasumigaura River Office of MLIT (Ministry of Land, Infrastructure and Transport, Government of Japan) and the Japan Water Agency for permitting the use of plant materials and their experiment station for our hand-pollination experiment. We also thank J. Nishihiro, F. Ishihama, M. Honjo, and two anonymous reviewers for their valuable comments on the manuscript. This research was partly supported by a Grant-in-Aid for Fellows of the Japan Society for the Promotion of Science (17-52322).
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