Species diversity in haploid dominat plant species-research on the inter-relationship between speciation and morphological diversification

苔藓植物的生活史以配子体为主，在陆生植物中具有独特性。因此，突变引起的基因型变化直接表现为表型表达。在此基础上，本课题进行了以下两方面的研究：1.藓类植物形态特征的演化及其对物种形成的贡献我们对分布广泛的稀有藓类植物Dixonia thumeoides进行了遗传学和形态学分析，了解到尽管在空间上分离的地方居群中存在形态变异，但遗传多样性很小.本研究以杜氏盾叶薯蓣复合体为材料，探讨了形态演化在肝脏物种形成中的作用，沿着染色体变化。已知硬毛杜氏菌具有其单倍体、二倍体和三倍体变体，并且已被视为包括在形态特征上具有广泛变异的单一物种。通过形态学、染色体数目、12个位点的等位酶谱和rbcL与atpB互编码区的分子证据分析，发现：（1）在二倍体中，存在着11个以上的“种”，遗传距离大于0.3，这些“种”不仅具有独特的形态特征，而且可以通过atpB-rbcL序列差异来区分。有趣的是，在日本群体中，二倍体和三倍体具有与单倍体不同的遗传特征，因此可能不是从单倍体祖先中衍生出简单的染色体复制。这一假说也得到了二倍体和三倍体是异源多倍体的事实的支持。目前已知的唯一例外是夏威夷岛的二倍体，它们是同源倍体，在每个基因座上共享所有等位基因。

Bryophytes have gametophyte-dominant life history and thus are unique among land plants. As a result, any changes in genotypes by mutation directly appear as phenotype expression. In this sequence, we conducted the following two researches in this project :1. Evolution of morphological features and its contribution on speciation in mossesWe conducted genetical and morphological analyses on the very rare, widely distributed moss species, Dixonia thamnioides, and knew that there was only a little genetical diversification in spite of morphological variation among spatially disjunct local populations.2. Investigation on the role of morphological evolution in speciation in hepatics, along with chromosomal changes.We conducted this research using Dumortiera hirusta complex. Dumortiera hirsuta has been known with its mono-, di-, and tri-ploids variants and have been treated as comprising a single species with wide variation in morphological features. Analyses on morphology, chromosome numbers, allozyme patterns with 12 loci, and molecular evidence of intercoding region between rbcL and atpB revealed the following facts :(1)Among monoploids, there exist more than eleven "species", recognizing with genetic distance more than 0.3.Each of these "species" not only has unique morphological features, but also can be distinguished by atpB- rbcL sequence differences. It is interesting that among Japanese populations di- and tri-ploids have different genetical features from monoploids and thus may not derived simple duplication of chromosome from monoploid ancestor. This hypothesis also supported by the fact that di- and tri-ploids are allopolyploid. The single exception as far as known is the diploids of Hawaii Island, which are autoploid and share all alleles in every loci.