open access

https://doi.org/10.14943/doctoral.k13547

https://hdl.handle.net/2115/87907

外来カワマスと在来アメマスにおける浸透交雑の存続機構

英語

2019-03-25

Hokkaido University

97p.

Human-mediated hybridization is one of the most serious threats to native taxa. Introgressive hybridization of native species with non-native species can cause the breakdown of inherent gene complexes and ecological adaptations in native populations. This breakdown can pose a major threat to the persistence of rare or endangered species, yet the fitness consequences of introgression and their determining factors have not been fully evaluated in the wild. I am investigating factors affecting the spread and/or sustainability of introgression between introduced brook trout (Salvelinus fontinalis) and native white-spotted charr (S. leucomaenis) in the upper Sorachi River system, Hokkaido, Japan. The fundamental questions of my doctoral work are: how long can non-native genes be sustained and what factors can contribute to sustain the introgression? To answer these questions, I first assessed the distributional pattern and its temporal changes of the parental species and their hybrids in the Sorachi River systems. The distributional range of introduced brook trout has decreased from 2003 to 2013, but introgression has nevertheless occurred during this period. Secondly, I quantified the reproductive success of parental species and their hybrids in a wild population, and also tested whether male’s reproductive characteristics, such as elongated jaws and deeper bodies, affect hybrid fitness. These characteristics should influence male-male interactions. The results of parentage analysis suggest that the reproductive success of hybrids was lower than that of their parental species and that the male’s reproductive traits influence the fitness of hybrid males. Finally, I compared other fitness components (i.e. survival and growth) and movement between the hybrids and their parental species, using 1089 tagged individuals followed over 4 years. The survival and growth of hybrids were equivalent or even higher than those of their parental species. Also, hybrids showed high mobility similar to native charr, while brook trout showed the lowest mobility. Together, these results suggest that despite a decreasing distributional range and low mobility, non-native brook trout can pose a threat to native white-spotted charr through introgressive hybridization.

2019-03-25

甲第13547号

博士(環境科学)

(主査) 准教授 小泉 逸郎, 特任教授 高田 壯則, 教授 野田 隆史, 主任研究員 森田 健太郎（国立研究開発法人水産研究・教育機構 北海道区水産研究所）

環境科学院（生物圏科学専攻）

博士論文

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