3种同域分布的杓兰属植物的种子及杂交种子特征分析

杂交种子研究在一定程度上能说明是否存在杂种不活机制，在植物生殖隔离研究中具有重要意义。通过对同域分布的西藏杓兰(Cypripedium tibeticum)、黄花杓兰(C.flavum)和褐花杓兰(C.calcicola)的自交、异交、杂交种子的形态特征及活性进行分析，发现3种杓兰属植物两两之间均可产生杂交种子，且杂交种子活性较高，杂交种子与其他处理所得种子的外观、表面纹饰无显著性差异；种子宽度、种子长度、有胚率、着色率并没有比自交或异交种子显著低。这一结果表明这3种同域杓兰属植物种与种之间具有相当高的亲和性，它们之间不存在明显的杂种不活机制。黄花杓兰与西藏杓兰或褐花杓兰间的传粉者大小明显不同,黄花杓兰由丽蝇和熊蜂工蜂传粉，而西藏杓兰和褐花杓兰由体形较大的熊蜂蜂王传粉，传粉者隔离已使得它们之间的物种界限比较清晰，因此已经没有必要再产生杂种不活等其他隔离机制。而西藏杓兰与褐花杓兰的传粉者相同，又没有明显的杂种不活隔离机制，暗示它们之间有其他合子后隔离机制或应将其合并为一个种。

Characteristics of Seeds and Hybrid Seeds in Three Sympatric Cypripedium Species

It is important to study hybrid seeds because it will illuminate hybrid inviability and reproductive isolation mechanism between plant species. Morphological characteristics and viability of seeds derived from self-pollination, cross-pollination and hybridization were analyzed in three sympatric Cypripedium species. Hybrid seeds with high viability were successfully obtained from sympatric plants C.flavum, C.tibeticum and C.calcicola. They were not significantly different in seed shape, surface sculpture compared with seeds from self-pollination and cross-pollination. The width, length, embryo ratio and pigmentation ratio of hybrid seeds were not significantly lower than those of seeds from self-pollination and cross-pollination. The results suggested that three sympatric Cypripedium species could be hybrid compatible and that hybrid inviability could not be the main reason of isolation among them. It was not necessary to produce other isolation mechanisms because pollinators with different sizes functioned as the main isolation mechanism between C.flavum and C.tibeticum or C.calcicola. However, with the same pollinators and hybrid viability, C.tibeticum or C.calcicola would produce other isolation mechanisms or they should be combined into one species.