CIBIO, University of Porto, Campus Agrario de Vairao, 4485-661 Vairao, Portugal.
Am J Bot. 2009 Jul;96(7):1262-73. doi: 10.3732/ajb.0800345.
Polyploidy has been ubiquitous in plant evolution and is thought to be an important engine of biodiversity that facilitates speciation, adaptation, and range expansion. Polyploid species can exhibit higher ecological tolerance than their progenitor species. For allotetraploid species, this higher tolerance is often attributed to the existence of heterosis resulting from entire genome duplication. However, multiple origins of allopolyploid species may further promote their ecological success by providing genetic variability in ecological traits underlying local adaptation and range expansion. Here we show in a group of allopolyploid species in the genus Aegilops that range size and abundance are correlated with the number of inferred origins. We found that allopolyploid Aegilops spp. contain multiple chloroplast haplotypes, each identical to haplotypes of the diploid progenitor species, indicating multiple origins as the major source of variation. The number of inferred origins in each allopolyploid species was correlated to the total area occupied by the allopolyploid and the tendency for the species to be common. Additionally, we found differences in ecological tolerance among independent origins in Aegilops triuncialis. These results strongly support the hypothesis that the introduction of genetic variability by multiple origins can increase the ecological amplitude and evolutionary success of allopolyploid species.
多倍体在植物进化中普遍存在，被认为是生物多样性的重要引擎，促进了物种形成、适应和分布范围的扩大。多倍体物种比其祖先物种表现出更高的生态耐受性。对于异源四倍体物种，这种更高的耐受性通常归因于整个基因组复制产生的杂种优势的存在。然而，异源多倍体物种的多个起源可能通过为适应局部环境和分布范围扩张的生态特征提供遗传变异性，进一步促进其生态成功。在这里，我们在一组普通小麦属的异源多倍体物种中表明，分布范围大小和丰度与推断的起源数量相关。我们发现，异源多倍体普通小麦属含有多个叶绿体单倍型，每个单倍型与二倍体祖先物种的单倍型相同，表明多起源是变异的主要来源。每个异源多倍体物种的推断起源数量与异源多倍体占据的总面积和物种常见性呈正相关。此外，我们还发现了在 Aegilops triuncialis 中独立起源之间的生态耐受性差异。这些结果强烈支持了以下假设，即多个起源引入遗传变异性可以增加异源多倍体物种的生态幅度和进化成功。
