Gehrke Berit, Linder H Peter
Institute for Systematic Botany, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland.
Proc Biol Sci. 2009 Jul 22;276(1667):2657-65. doi: 10.1098/rspb.2009.0334. Epub 2009 Apr 29.
The composition of isolated floras has long been thought to be the result of relatively rare long-distance dispersal events. However, it has recently become apparent that the recruitment of lineages may be relatively easy and that many dispersal events from distant but suitable habitats have occurred, even at an infraspecific level. The evolution of the flora on the high mountains of Africa has been attributed to the recruitment of taxa not only from the African lowland flora or the Cape Floristic Region, but also to a large extent from other areas with temperate climates. We used the species rich, pan-temperate genera Carex, Ranunculus and Alchemilla to explore patterns in the number of recruitment events and region of origin. Molecular phylogenetic analyses, parametric bootstrapping and ancestral area optimizations under parsimony indicate that there has been a high number of colonization events of Carex and Ranunculus into Africa, but only two introductions of Alchemilla. Most of the colonization events have been derived from Holarctic ancestors. Backward dispersal out of Africa seems to be extremely rare. Thus, repeated colonization from the Northern Hemisphere in combination with in situ radiation has played an important role in the composition of the flora of African high mountains.
长期以来，人们一直认为隔离植物区系的组成是相对罕见的长距离扩散事件的结果。然而，最近有一点变得很明显，即谱系的招募可能相对容易，而且即使在种下水平，也发生了许多来自遥远但适宜栖息地的扩散事件。非洲高山植物区系的演化不仅归因于从非洲低地植物区系或开普植物区招募类群，而且在很大程度上还归因于来自其他温带地区的类群。我们利用物种丰富的泛温带属苔草属、毛茛属和羽衣草属，来探究招募事件的数量和起源区域的模式。分子系统发育分析、参数自展法和简约性原则下的祖先区域优化表明，苔草属和毛茛属有大量定殖到非洲的事件，但羽衣草属只有两次引入。大多数定殖事件都源自全北区祖先。从非洲反向扩散似乎极为罕见。因此，北半球的反复定殖与原地辐射相结合，在非洲高山植物区系的组成中发挥了重要作用。
