Department of Plant Sciences, University of Oxford, Oxford, UK.
J Evol Biol. 2011 Jan;24(1):1-11. doi: 10.1111/j.1420-9101.2010.02128.x. Epub 2010 Nov 2.
Island radiations are often regarded as natural laboratories that allow us to study evolution in action. The genus Schiedea (Caryophyllaceae) is one of the largest radiations of angiosperms in the Hawaiian Islands, and Schiedea globosa is one of the few species in the genus to be found on more than one of the main islands. DNA sequences from nineteen nuclear and three chloroplast regions show a pattern of colonization from older to younger islands (west to east), with a concomitant decrease in genetic diversity eastwards (π=0.53% for O'ahu, 0.43% for Moloka'i and 0.36% for Maui). While polymorphisms in the maternally inherited chloroplast have become fixed on different islands (F(ST)=0.804), significant gene flow between islands is inferred for the nuclear genome (F(ST)=0.270). This gene flow appears to be uneven, with most gene flow outwards from the central island. The extent of inter-island gene flow through wind pollination was assessed in an isolation-migration framework; the inferred rate, c. 1 migrant per generation, may be sufficient to prevent divergence of S. globosa populations and ensure cohesion of the species following the colonization of new islands.
岛屿辐射通常被视为自然实验室，使我们能够研究进化的实际过程。石竹科 Schiedea 属是夏威夷群岛中被子植物最大辐射之一，而 Schiedea globosa 是该属中为数不多的在多个主要岛屿上都有发现的物种之一。来自 19 个核和 3 个叶绿体区域的 DNA 序列显示出从较老岛屿（向西）到较新岛屿（向东）的殖民模式，同时遗传多样性向东减少（O'ahu 的 π=0.53%，Moloka'i 的 π=0.43%，Maui 的 π=0.36%）。虽然母系遗传的叶绿体中的多态性已经在不同的岛屿上固定下来（F(ST)=0.804），但对核基因组来说，推断出了岛屿之间的显著基因流（F(ST)=0.270）。这种基因流似乎是不均匀的，大多数基因流是从中心岛向外流出。在隔离-迁移框架中评估了通过风授粉的岛屿间基因流程度；推断的速率约为每代 1 个移徙者，这可能足以防止 S. globosa 种群的分化，并确保在新岛屿殖民后物种的凝聚力。
