Nees-Institute for Biodiversity of Plants, University of Bonn, 53115, Bonn, Germany.
Biol Rev Camb Philos Soc. 2019 Oct;94(5):1658-1671. doi: 10.1111/brv.12520. Epub 2019 May 3.
Thousands of plant species worldwide are dependent on birds for pollination. While the ecology and evolution of interactions between specialist nectarivorous birds and the plants they pollinate is relatively well understood, very little is known on pollination by generalist birds. The flower characters of this pollination syndrome are clearly defined but the geographical distribution patterns, habitat preferences and ecological factors driving the evolution of generalist-bird-pollinated plant species have never been analysed. Herein I provide an overview, compare the distribution of character states for plants growing on continents with those occurring on oceanic islands and discuss the environmental factors driving the evolution of both groups. The ecological niches of generalist-bird-pollinated plant species differ: on continents these plants mainly occur in habitats with pronounced climatic seasonality whereas on islands generalist-bird-pollinated plant species mainly occur in evergreen forests. Further, on continents generalist-bird-pollinated plant species are mostly shrubs and other large woody species producing numerous flowers with a self-incompatible reproductive system, while on islands they are mostly small shrubs producing fewer flowers and are self-compatible. This difference in character states indicates that diverging ecological factors are likely to have driven the evolution of these groups: on continents, plants that evolved generalist bird pollination escape from pollinator groups that tend to maintain self-pollination by installing feeding territories in single flowering trees or shrubs, such as social bees or specialist nectarivorous birds. This pattern is more pronounced in the New compared to the Old World. By contrast, on islands, plants evolved generalist bird pollination as an adaptation to birds as a reliable pollinator group, a pattern previously known from plants pollinated by specialist nectarivorous birds in tropical mountain ranges. Additionally, I discuss the evolutionary origins of bird pollination systems in comparison to systems involving specialist nectarivorous birds and reconstruct the bird pollination system of Hawaii, which may represent an intermediate between a specialist and generalist bird pollination system. I also discuss the interesting case of Australia, where it is difficult to distinguish between specialist and generalist bird pollination systems.
全球有数千种植物依赖鸟类传粉。虽然专食花蜜的鸟类与它们传粉的植物之间的相互作用的生态和进化相对较为了解，但对一般性鸟类传粉的了解却很少。这种传粉综合征的花特征定义明确，但尚未分析一般性鸟类传粉植物物种的地理分布模式、生境偏好和生态因素。本文提供了一个概述，比较了生长在大陆上的植物的特征状态分布与生长在海洋岛屿上的植物的特征状态分布，并讨论了驱动这两组植物进化的环境因素。一般性鸟类传粉植物物种的生态位不同：在大陆上，这些植物主要出现在气候季节性明显的生境中，而在岛屿上，一般性鸟类传粉植物物种主要出现在常绿森林中。此外，在大陆上，一般性鸟类传粉植物物种主要是灌木和其他大型木本植物，它们产生许多具有自交不亲和生殖系统的花朵，而在岛屿上，它们主要是产生较少花朵且自交亲和的小灌木。这些特征状态的差异表明，不同的生态因素可能推动了这两组植物的进化：在大陆上，进化出一般性鸟类传粉的植物逃避了那些倾向于通过在单株开花的树木或灌木上建立取食领地来维持自交的传粉者群体，例如社会性蜜蜂或专食花蜜的鸟类。这种模式在新世界比旧世界更为明显。相比之下，在岛屿上，植物进化出一般性鸟类传粉是对鸟类作为可靠传粉者的一种适应，这种模式以前在热带山脉中由专食花蜜的鸟类传粉的植物中有所了解。此外，我还讨论了与专食花蜜的鸟类传粉系统相比，鸟类传粉系统的进化起源，并重建了夏威夷的鸟类传粉系统，该系统可能代表了专食和一般性鸟类传粉系统之间的中间状态。我还讨论了澳大利亚的有趣案例，在那里很难区分专食和一般性鸟类传粉系统。
