Pieper Sara, Dorken Marcel, Freeland Joanna
Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, Canada.
Department of Biology, Trent University, Peterborough, ON, Canada.
Heredity (Edinb). 2020 Jun;124(6):714-725. doi: 10.1038/s41437-020-0307-y. Epub 2020 Mar 18.
Traditional models of hybrid zones have assumed relatively low hybrid fitness, and thus focussed more on interspecific gene flow than on hybrid dispersal. Therefore, when hybrids have high fitness and the potential for autonomous dispersal, we have limited understanding of whether hybrid dispersal or repeated local hybrid formation is more important for maintaining hybrid zones. The invasive hybrid cattail Typha × glauca occupies an extensive hybrid zone in northeastern North America where it is sympatric with its progenitors T. latifolia and T. angustifolia. We characterized genetic diversity and genetic structure of the three taxa across a broad spatial scale where the maternal parent is relatively rare, and tested the hypothesis that the hybrid shows stronger evidence of gene flow than its progenitor species, particularly among disturbed sites (ditches) compared with established wetlands. Support for this hypothesis would suggest that dispersal, rather than repeated local formation, is more important for maintaining hybrid zones. Within each taxon, genetic differentiation among ditches was comparable to that among wetlands, although clonal richness was consistently greater in ditches, suggesting more frequent seed establishment. Genetic structure across sites was more pronounced in the hybrid compared with either progenitor species. Overall, our data reflect relatively low gene flow in hybrids, and suggest that hybrids are more likely to be created in situ than to be introduced from other sites. Despite the high fitness of invasive T. × glauca and its potential for autonomy, local processes appear more important than dispersal in maintaining this hybrid zone.
传统的杂交带模型假定杂种适合度相对较低，因此更多地关注种间基因流而非杂种扩散。所以，当杂种具有高适合度和自主扩散潜力时，我们对于杂种扩散或反复的本地杂种形成在维持杂交带方面哪个更重要的理解有限。入侵性杂种香蒲（Typha × glauca）在北美东北部占据了一个广阔的杂交带，在那里它与其亲本物种宽叶香蒲（T. latifolia）和狭叶香蒲（T. angustifolia）同域分布。我们在一个广阔的空间尺度上对这三个类群的遗传多样性和遗传结构进行了表征，在这个尺度上母本相对稀少，并检验了这样一个假设：杂种比其亲本物种表现出更强的基因流证据，特别是在受干扰的地点（沟渠）与已建立的湿地相比。对这一假设的支持将表明，扩散而非反复的本地形成对于维持杂交带更为重要。在每个类群中，沟渠间的遗传分化与湿地间的相当，尽管沟渠中的克隆丰富度一直更高，这表明种子建立更频繁。与任何一个亲本物种相比，杂交种在各地点间的遗传结构更为明显。总体而言，我们的数据反映出杂种中的基因流相对较低，并表明杂种更有可能是在原地产生的，而不是从其他地点引入的。尽管入侵性的T. × glauca具有高适合度及其自主潜力，但在维持这个杂交带方面，本地过程似乎比扩散更为重要。
