Meudt Heidi M, Albach Dirk C, Tanentzap Andrew J, Igea Javier, Newmarch Sophie C, Brandt Angela J, Lee William G, Tate Jennifer A
Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand.
Institute of Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany.
Front Plant Sci. 2021 Mar 4;12:637214. doi: 10.3389/fpls.2021.637214. eCollection 2021.
Whole genome duplication or polyploidy is widespread among floras globally, but traditionally has been thought to have played a minor role in the evolution of island biodiversity, based on the low proportion of polyploid taxa present. We investigate five island systems (Juan Fernández, Galápagos, Canary Islands, Hawaiian Islands, and New Zealand) to test whether polyploidy (i) enhances or hinders diversification on islands and (ii) is an intrinsic feature of a lineage or an attribute that emerges in island environments. These island systems are diverse in their origins, geographic and latitudinal distributions, levels of plant species endemism (37% in the Galapagos to 88% in the Hawaiian Islands), and ploidy levels, and taken together are representative of islands more generally. We compiled data for vascular plants and summarized information for each genus on each island system, including the total number of species (native and endemic), generic endemicity, chromosome numbers, genome size, and ploidy levels. Dated phylogenies were used to infer lineage age, number of colonization events, and change in ploidy level relative to the non-island sister lineage. Using phylogenetic path analysis, we then tested how the diversification of endemic lineages varied with the direct and indirect effects of polyploidy (presence of polyploidy, time on island, polyploidization near colonization, colonizer pool size) and other lineage traits not associated with polyploidy (time on island, colonizer pool size, repeat colonization). Diploid and tetraploid were the most common ploidy levels across all islands, with the highest ploidy levels (>8) recorded for the Canary Islands (12) and New Zealand (20). Overall, we found that endemic diversification of our focal island floras was shaped by polyploidy in many cases and certainly others still to be detected considering the lack of data in many lineages. Polyploid speciation on the islands was enhanced by a larger source of potential congeneric colonists and a change in ploidy level compared to overseas sister taxa.
全基因组复制或多倍体现象在全球植物区系中广泛存在，但传统观点认为，基于多倍体分类群所占比例较低，它在岛屿生物多样性的进化中所起的作用较小。我们研究了五个岛屿系统（胡安·费尔南德斯群岛、加拉帕戈斯群岛、加那利群岛、夏威夷群岛和新西兰），以检验多倍体是否（i）促进或阻碍岛屿上的物种分化，以及（ii）是一个谱系的固有特征还是在岛屿环境中出现的一种属性。这些岛屿系统在起源、地理和纬度分布、植物物种特有性水平（加拉帕戈斯群岛为37%，夏威夷群岛为88%）以及倍性水平方面各不相同，总体上代表了更普遍的岛屿情况。我们收集了维管植物的数据，并总结了每个岛屿系统中每个属的信息，包括物种总数（本地种和特有种）、属的特有性、染色体数目、基因组大小和倍性水平。利用有时间标定的系统发育树来推断谱系年龄、殖民事件数量以及相对于非岛屿姐妹谱系的倍性水平变化。然后，我们使用系统发育路径分析来检验特有谱系的分化如何随多倍体的直接和间接影响（多倍体的存在、在岛屿上的时间、殖民附近的多倍体化、殖民者库大小）以及其他与多倍体无关的谱系特征（在岛屿上的时间、殖民者库大小、重复殖民）而变化。二倍体和四倍体是所有岛屿上最常见的倍性水平，加那利群岛（12）和新西兰（20）记录到的最高倍性水平（>8）。总体而言，我们发现，在许多情况下，我们所关注的岛屿植物区系的特有分化是由多倍体塑造的，而且考虑到许多谱系缺乏数据，肯定还有其他情况有待发现。与海外姐妹类群相比，潜在同属殖民者来源更广以及倍性水平的变化促进了岛屿上的多倍体物种形成。
