杠杆状雄蕊及其进化生态学意义

A review of the evolutionary and ecological significance of lever-like stamens

对被子植物一类特化雄蕊——杠杆状雄蕊的结构多样性及其进化生态学意义进行了归纳总结。植物的花在进化过程中,常会发生雄蕊群的改变,包括雄蕊数目及其形态结构的变化,同时雄蕊功能也会发生相应的适应性转变。杠杆状雄蕊是指结构特化为杠杆状或距状,在传粉过程中具有类似杠杆功能的一类特化的雄蕊类型。目前,已在唇形科不同亚科以及姜科6个属中发现杠杆状雄蕊,根据其结构和形态发生方式总体上可分为2大类:一类是唇形科中以鼠尾草属(Salvia)为代表的,由2个可育雄蕊平行发育、药隔组织增长所形成的杠杆状雄蕊;另一类是姜科植物中由一个可育雄蕊特化形成的带有距状附属体的雄蕊类型。在生态功能上,两类雄蕊均能通过传粉者推动其距状下臂做杠杆运动进行传粉,被认为是一种促进异交的传粉机制,可通过精确传粉和花粉分发等途径影响植物的繁殖成功。杠杆状雄蕊在不同的类群中是独立起源与进化的;仅在唇形科鼠尾草属中,杠杆状雄蕊发生了3次独立进化,而且它可能是触发该属物种适应性辐射的关键性状。将来需在宏观进化和微观进化两个水平深入探讨杠杆状雄蕊的进化生态学意义。

We review the structural diversity and evolutionary significance of a type of highly modified stamen that is lever-like or spurred and can function as lever during pollination. Evolutionary changes of the androecium in stamen number and morphology often take place during floral evolution, shifting from pollen production to new functions. Lever-like stamens have been described in several subfamilies of Lamiaceae and six genera of Zingiberaceae. There are two types. One is derived from connective elongation and is largely structured by two parallel developed stamens; it occurs in the Lamiaceae, typically Salvia. The other is modified from one developed stamen and occurs in the Zingiberaceae. Both types have a similar role in pollination in that pollinators have to push the lower arm of the staminal lever into the corolla tube for nectar and consequently load pollen on their backs; this is widely regarded as a mechanism of facilitating crossing-pollination and can affect reproductive success via precise pollination, pollen dispensing, etc. These stamens independently originated and evolved in different taxa. For example, there have been three independent evolutions in Salvia, and this has been presumed a key innovation driving species＇ radiation within the genus. Future research is needed at the levels of both macro- and micro-evolution to fully understand evolutionary and ecological significance of lever-like stamens.