心启兰属(Chenorchis)-兰科一新属及其蚂蚁传粉的生态策略

Chenorchis:a new orchid genus and its eco-strategy of ant pollination

在云南的高黎贡山的亚热带区域发现了具热带兰科种类特征的兰科新属心启兰属(Chenorchis)(属模式种心启兰C.singchii)。该属种具有附生、单轴生长,花粉团坚硬,粘盘柄存在等兰科较为进化的特征无疑是热带万代兰族(Trib.Vandeae)的成员,与鸟舌兰属(Ascocentrum)和槽舌兰属(Holcoglossum)有亲缘关系。区别点在于新属的唇瓣不具附属物;侧裂片生于中裂片两侧而非距口两侧;柱头腔大;蕊喙甚大,明显宽于蕊柱,向下伸展;花粉团具明显的柄,附着于一个共同的粘盘柄近顶端内弯处。系统学分析结果显示其祖先可能来自热带,因环境改变演化为新属种,体现了被子植物分化的主要动力可能是开拓了更多的生态学机遇;进一步的繁殖生态学特别是传粉机制和繁育系统的检测表明,该物种发展出多个促进自交或近交的机制,如选择有切胸蚁(Temnothoraxsp.)栖息的生境,利用蚂蚁近距离传粉;花朵同时开放增加同株异花授粉发生机率;种子有效的就近散播和生长,产生局域拥挤效应以增加近亲繁殖的可能,这些适应性改变成为它们在亚热带生存下来的必要条件,特殊的生活史(繁殖)策略展示了它作为迁移种通过迅速增长抢占生境,自动地将遗传基因传递给后代以保持对当地的适应性,花序进化出大量花并同时开放便于同株异花传粉是成功开拓生境的一种对策,其意义的延伸可能为植物的性的产生是进化上应对生境波动的权衡提供一个证据。

Chenorchis, a new orchid genus, based on C. singchii, with tropical orchid features, was found in subtropical regions of Gaoligong Mountain in Yunnan Province, China. This taxon undoubtedly belongs to Trib. Vandeae with its comparatively advanced characteristics： epiphytic, monopodial, and with very hard pollinia, and long stipe; it is akin to Ascocentrum and Holcoglossum, from which it differs by its lip lacking appendage, with side-lobes arising from both sides of the mid-lobe rather than the entrance to the spur; stigmatic cave large; rostellum very large, conspicuously broader than column, spreading downward; pollinia each with a distinct caudicle attached to the incurved subterminal portion of a common stipe. Phylogenetic analysis shows that it may be of tropical origin regions and evolve a new genus for changed environmental, indicating that the main motivation of Angiosperms differentiation is to bring forth more ecological opportunities ; a further examination of reproductive ecology, especially pollination mechanism and breeding system, proved that this species has formed many mechanism to promote selfing and inbreeding. For instance, symbiosis with ants, （Temnothorax sp. ）, utilization of ants for short-distant pollination, flowers opening simultaneously to increase the frequency of geitonogamy, efficient dispersal and growth of seeds, crowed community to improve the possibility of inbreeding. All the above adaptive changes turn into necessary conditions for their survival in subtropical regions. And the reproductive strategy of this unique life history shows that this immigrant species autonomously passes the genes on to future generations to remain their adaptability, by quickly occupying the habitat. The success in habitat expansion strategy, of which inflorescence produces a lot of flowers to facilitate geitonogamy, and its significance may extend to provide an evidence that the occurrence of plant＇s sex results from the trade-offs of the fluctuation of habitat in evolution.