Goldblatt Peter, Manning John C
B. A. Krukoff Curator of African Botany, Missouri Botanical Garden, PO Box 299, St Louis, MO 63166, USA.
Ann Bot. 2006 Mar;97(3):317-44. doi: 10.1093/aob/mcj040. Epub 2005 Dec 23.
Seventeen distinct pollination systems are known for genera of sub-Saharan African Iridaceae and recurrent shifts in pollination system have evolved in those with ten or more species. Pollination by long-tongued anthophorine bees foraging for nectar and coincidentally acquiring pollen on some part of their bodies is the inferred ancestral pollination strategy for most genera of the large subfamilies Iridoideae and Crocoideae and may be ancestral for the latter. Derived strategies include pollination by long-proboscid flies, large butterflies, night-flying hovering and settling moths, hopliine beetles and sunbirds. Bee pollination is diverse, with active pollen collection by female bees occurring in several genera, vibratile systems in a few and non-volatile oil as a reward in one species. Long-proboscid fly pollination, which is apparently restricted to southern Africa, includes four separate syndromes using different sets of flies and plant species in different parts of the subcontinent. Small numbers of species use bibionid flies, short-proboscid flies or wasps for their pollination; only about 2 % of species use multiple pollinators and can be described as generalists.
Using pollination observations for 375 species and based on repeated patterns of floral attractants and rewards, we infer pollination mechanisms for an additional 610 species. Matching pollination system to phylogeny or what is known about species relationships based on shared derived features, we infer repeated shifts in pollination system in some genera, as frequently as one shift for every five or six species of southern African Babiana or Gladiolus. Specialized systems using pollinators of one pollination group, or even a single pollinator species are the rule in the family. Shifts in pollination system are more frequent in genera of Crocoideae that have bilaterally symmetric flowers and a perianth tube, features that promote adaptive radiation by facilitating precise shifts in pollen placement, in conjunction with changes in flower colour, scent and tube length.
Diversity of pollination systems explains in part the huge species diversity of Iridaceae in sub-Saharan Africa, and permits species packing locally. Pollination shifts are, however, seen as playing a secondary role in speciation by promoting reproductive isolation in peripheral, ecologically distinct populations in areas of diverse topography, climate and soils. Pollination of Iridaceae in Eurasia and the New World, where the family is also well represented, is poorly studied but appears less diverse, although pollination by both pollen- and oil-collecting bees is frequent and bird pollination rare.
已知撒哈拉以南非洲鸢尾科各属有17种不同的授粉系统，在拥有10种或更多物种的属中，授粉系统发生了反复的转变。长舌花蜂科蜜蜂为获取花蜜觅食，其身体某些部位会偶然沾上花粉，这种授粉方式被推断为鸢尾亚科和番红花亚科大多数属的原始授粉策略，对后者来说可能也是原始的。衍生策略包括长喙蝇授粉、大型蝴蝶授粉、夜间飞行的悬停和停歇蛾授粉、长角象鼻虫授粉以及太阳鸟授粉。蜜蜂授粉方式多样，一些属的雌蜂会主动采集花粉，少数属有震动传粉系统，还有一个物种以非挥发性油作为回报。长喙蝇授粉显然仅限于非洲南部，包括四种不同的综合症，在该次大陆不同地区使用不同的蝇类和植物物种组合。少数物种利用毛蚊科蝇、短喙蝇或黄蜂进行授粉；只有约2%的物种使用多种传粉者，可以被描述为泛化种。
利用对375个物种的授粉观察，并基于花的引诱剂和回报的重复模式，我们推断出另外610个物种授粉机制。将授粉系统与系统发育或基于共同衍生特征的物种关系所知内容相匹配，我们推断出一些属的授粉系统发生了反复转变，频率高达南非鸢尾属或唐菖蒲属每五六个物种就有一次转变。使用单一授粉群体的传粉者甚至单一传粉者物种的特化系统是该科的常态。在具有两侧对称花朵和花被管的番红花亚科属中，授粉系统的转变更为频繁，这些特征通过促进花粉放置的精确转变，结合花色、气味和花管长度的变化，促进了适应性辐射。
授粉系统的多样性部分解释了撒哈拉以南非洲鸢尾科巨大的物种多样性，并允许物种在当地密集分布。然而授粉转变被视为在物种形成中起次要作用，通过促进不同地形、气候和土壤地区边缘生态上不同的种群的生殖隔离。在欧亚大陆和新大陆，鸢尾科也有大量代表，但对其授粉情况研究较少，不过花粉采集蜂和油采集蜂授粉都很常见，而鸟类授粉很少见。
