Westerkamp Christian, Classen-Bockhoff Regine
Agronomia, Campus do Cariri, Universidade Federal do Ceará, Crato, CE, Brazil.
Ann Bot. 2007 Aug;100(2):361-74. doi: 10.1093/aob/mcm123.
Bilabiate flowers have evolved in many lineages of the angiosperms, thus representing a convincing example of parallel evolution. Similar to keel blossoms, they have obviously evolved in order to protect pollen against pollen-collecting bees. Although many examples are known, a comprehensive survey on floral diversity and functional constraints of bilabiate flowers is lacking. Here, the concept is widened and described as a general pattern.
The present paper is a conceptional review including personal observations of the authors. To form a survey on the diversity of bilabiate blossoms, a search was made for examples across the angiosperms and these were combined with personal observations collected during the last 25 years, coupled with knowledge from the literature. New functional terms are introduced that are independent of morphological and taxonomic associations.
Bilabiate constructions occur in at least 38 angiosperm families. They are characterized by dorsiventral organization and dorsal pollen transfer. They are most often realised on the level of a single flower, but may also be present in an inflorescence or as part of a so-called 'walk-around flower'. Interestingly, in functional terms all nototribic blossoms represent bilabiate constructions. The great majority of specialized bee-flowers can thus be included under bilabiate and keel blossoms. The syndrome introduced here, however, also paves the way for the inclusion of larger animals such as birds and bats. The most important evolutionary trends appear to be in the saving of pollen and the precision of its transfer. With special reference to the Lamiales, selected examples of bilabiate flowers are presented and their functional significance is discussed.
Bilabiate blossoms protect their pollen against pollen-collecting bees and at the same time render their pollination more precisely. The huge diversity of realised forms indicate the high selection pressure towards the bilabiate syndrome. As bees are very inventive, however, bilabiate constructions will not represent the ultimate response to bees.
唇形花在被子植物的许多谱系中都有进化，因此是平行进化的一个有说服力的例子。与龙骨花类似，它们显然是为了保护花粉免受采粉蜜蜂的侵害而进化的。尽管已知许多例子，但缺乏对唇形花的花多样性和功能限制的全面调查。在此，这一概念得到了扩展并被描述为一种普遍模式。
本文是一篇概念性综述，包括作者的个人观察。为了对唇形花的多样性进行调查，在被子植物中寻找了相关例子，并将其与过去25年收集的个人观察结果以及文献中的知识相结合。引入了独立于形态学和分类学关联的新功能术语。
唇形结构出现在至少38个被子植物科中。它们的特点是背腹组织和背部花粉传递。它们最常出现在单花水平，但也可能存在于花序中或作为所谓“游走花”的一部分。有趣的是，从功能角度来看，所有背向传粉的花都代表唇形结构。因此，绝大多数专门的蜜蜂花可以归入唇形花和龙骨花。然而，这里引入的综合征也为纳入鸟类和蝙蝠等更大的动物铺平了道路。最重要的进化趋势似乎是在花粉保存和花粉传递的精确性方面。特别提到唇形目，展示了唇形花的选定例子并讨论了它们的功能意义。
唇形花保护其花粉免受采粉蜜蜂的侵害，同时使其授粉更加精确。实现形式的巨大多样性表明对唇形综合征有很高的选择压力。然而，由于蜜蜂非常有创造性，唇形结构不会是对蜜蜂的最终应对方式。
