School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg 3209, South Africa.
Philos Trans R Soc Lond B Biol Sci. 2010 Feb 12;365(1539):499-516. doi: 10.1098/rstb.2009.0243.
The flora of southern Africa has exceptional species richness and endemism, making it an ideal system for studying the patterns and processes of evolutionary diversification. Using a wealth of recent case studies, I examine the evidence for pollinator-driven diversification in this flora. Pollination systems, which represent available niches for ecological diversification, are characterized in southern Africa by a high level of ecological and evolutionary specialization on the part of plants, and, in some cases, by pollinators as well. These systems are asymmetric, with entire plant guilds commonly specialized for a particular pollinator species or functional type, resulting in obvious convergent floral evolution among guild members. Identified modes of plant lineage diversification involving adaptation to pollinators in these guilds include (i) shifts between pollination systems, (ii) divergent use of the same pollinator, (iii) coevolution, (iv) trait tracking, and (v) floral mimicry of different model species. Microevolutionary studies confirm that pollinator shifts can be precipitated when a plant species encounters a novel pollinator fauna on its range margin, and macroevolutionary studies confirm frequent pollinator shifts associated with lineage diversification. As Darwin first noted, evolutionary specialization for particular pollinators, when resulting in ecological dependency, may increase the risk of plant extinction. I thus also consider the evidence that disturbance provokes pollination failure in some southern African plants with specialized pollination systems.
南非的植物区系具有异常丰富的物种多样性和特有性，使其成为研究进化多样化模式和过程的理想系统。利用大量最近的案例研究，我检查了在这个植物区系中授粉者驱动的多样化的证据。授粉系统代表了生态多样化的可用生态位，在南非，植物在生态和进化方面具有高度的专门化，在某些情况下，授粉者也是如此。这些系统是不对称的，整个植物类群通常专门为特定的授粉者物种或功能类型而专业化，导致类群成员之间明显的趋同花进化。在这些类群中，涉及适应授粉者的植物谱系多样化的模式包括（i）授粉系统之间的转变，（ii）相同授粉者的不同使用，（iii）共同进化，（iv）性状跟踪，以及（v）不同模式物种的花模拟。微观进化研究证实，当一个植物物种在其分布边缘遇到新的授粉者动物群时，授粉者的转变可以被引发，而宏观进化研究证实了与谱系多样化相关的频繁授粉者转变。正如达尔文最初指出的，对特定授粉者的进化专门化，如果导致生态依赖，可能会增加植物灭绝的风险。因此，我也考虑了一些证据，即干扰可能会导致一些南非具有专门授粉系统的植物授粉失败。
