Ecological and genetical mechanisms of hybrid speciation in the genus Trillium

延龄草属是具有代表性的温带林地成分之一，目前在北美和包括日本在内的东亚地区呈间断分布。该属由46种组成，其中10种已知分布于东亚。在这些东亚物种中，有8种分布在日本北海道。此外，根据染色体研究还得知，这8个种由3个种和5个杂交种和/或杂交衍生种组成，它们形成2x、3x、4x、6x多倍体系列。为了阐明东亚延龄草自然杂交和物种形成的生态机制，本文以三倍体延龄草为研究对象，它是克氏延龄草(T.kamtschaticum)和四倍体延龄草(T.tschonoskii)之间的天然杂交种。这种杂交物种通常发生在两个亲本物种共生的地方。本研究对三种延龄草的繁育系统、开花个体的空间分布格局和开花物候进行了田间考察，并进行了细胞质DNA的RFLP分析。结果表明，hagae主要来源于kamtschaticum(母本)和T.tschonoskii(父本)的杂交。

The genus Trillium is one of the representative temperate woodland elements which currently show disjunct distribution between North America and eastern Asia including Japan. The genus consists of 46 species and 10 species are known to occur in eastern Asia. Of those eastern Asiatic, species, eight species occur in Hokkaido, Japan. Furthemore, based on the chromosome studies, it has been also known that the eight species consist of three species and five hybrid and/or hybrid derivative species from putative hybridization among the three basic species, and they form polyploid series, 2x, 3x, 4x, 6x. By contrast, all of the North America species are known to be diploid.In order to clarify the ecological mechanisms of natural hybridization and speciation in the eastern Asiatic Trillium, I focused on T.*hagae (triploid species), which is a natural hybrid species between T.kamtschaticum (diploid species) and T.tschonoskii (tetraploid species). This hybrid species commonly occurs where both parental species grow sympatrically. In this study, breeding system, spatial distribution patterns of flowering individuals and flowering phenology of the three Trillium species were examined in the field, and RFLP analysis of cytoplasmic DNA was also employed. As a result, it was suggested that T.hagae is predominantly derived from the hybridization between T.kamtschaticum (maternal) and T.tschonoskii (paternal).