Cytological and molecular genetic studies on introgressive hybridizations among genus Arachniodes Blume (Dryopteridaceae; Pteridophyta)

本文从细胞学、形态学和分子遗传学等方面为日本蕨类植物Arachniodes Blume(鳞毛蕨科；蕨类植物)的二倍体(2n=82)种间的杂交提供了细胞学、形态学和分子遗传学证据。五个可能的天然杂交种，A.x tohtomiensis Sa.Kurata、中间种A.x intermedia Shimura(A.aristata(Forst.)Tindale x Sporadosora(Koze)Nakaike)、拟拟青杨A.x Simans(Ching)Ching、青杨A.x Tomitae Sa.Kurata和A.x Masakii Sa.在减数分裂中期I(32II~41II)显示高二价体形成，每个孢子囊产生正常形状的孢子。它们的孢子萌发率为20-50%，并生长到原生叶，形成雄蕊和颈卵器。在杂交种群体中，发现有几种植物具有其中一种的叶绿体单倍型和另一种的两位点等位基因。这样的个体只能通过F_1杂交种或后代杂交产生。该地点的形态变异模式与分子数据一致，我们的细胞学、形态和分子遗传学数据表明，该种群是一个杂交群。我们的数据证实了已知的唯一涉及亚洲温带蕨类植物的案例，其杂交已经在二倍体水平上超过了F1代。

We present cytological, morphological, and molecular genetic evidence for later-generation hybridization among several diploid (2n = 82) species of Arachniodes Blume (Dryopteridaceae; Pteridophyta) in Japan. Five putative natural hybrids, A. x tohtomiensis Sa. Kurata, A. x intermedia Shimura (A. aristata (Forst.) Tindale x sporadosora (Kunze) Nakaike), A. x simulans (Ching) Ching, A. x tomitae Sa. Kurata, and A. x masakii Sa. Kurata, displayed high bivalents formations at meiotic metaphase I, from 32II to 41II, and produced normal shaped 64 spores per sporangium. Their spores germinated at 20-50% and grew to prothallia that developed antheridia and archegonia. In a mixed-species population in which A. aristata and A. sporadosora grew together, several plants were found it have the chloroplastic haplotype of one of the species and the two-loci allozymatic genotype of the other. Such individuals can only have arisen via matings between F_1 hybrids or by later-generation hybridization. The pattern of morphological variation at this site is consistent with the molecular data, and our cytological, morphological, and molecular genetic data suggest that the population is a hybrid swarms. Our data confirm the only known case involving temperate-zone Asian pteridophytes where hybridization has gone beyond the F_1 generation at the diploid level.