Geng Shi-Lei, Chen Quan, Cai Wen-Li, Cao Ao-Cheng, Ou-Yang Can-Bin
College of Life Sciences, South China Agricultural University, Guangzhou 510642, China
College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
Ann Bot. 2017 Feb;119(3):457-464. doi: 10.1093/aob/mcw218. Epub 2016 Dec 27.
Roads as corridors of seed or fruit spatial dispersal have major impacts on the establishment and spread of invasive species, but their precise role in population genetic variation remains poorly understood. The South American weed Mikania micrantha has spread rapidly across southern China since its introduction to the Shenzhen area in 1984. This study investigated how its genetic diversity is distributed along highways, and whether highways have acted as corridors for the rapid expansion of M. micrantha METHODS: Twenty-seven roadside populations were sampled along four highways in southern China, and 787 samples were examined using 12 microsatellite markers. Variation in genetic diversity among populations was quantified and patterns of genetic differentiation were analysed.
A high level of genetic diversity was found at both the species and the population levels in this self-incompatible plant (expected heterozygosity = 0·497 and 0·477, respectively; allelic richness = 2·580 and 2·521, respectively). The Wright F-statistic value among populations (0·044, P < 0·01) and the analysis of molecular variance (91 % of genetic variation residing within populations, 9 % among populations within highways and 0 % among the four highways) showed a relatively low level of genetic differentiation among populations, while the principal coordinate and cluster analyses also indicated a lack of clear geographical genetic structure among populations. The calculated N value of 5·5 signifies strong gene flow.
The pattern of genetic variation is consistent with facilitated dispersal along highways. The genetic admixtures among the roadside populations imply the occurrence of multiple population introductions during colonization. The long-distance dispersal of seeds associated with vehicular transportation on highways may have played important roles in shaping the genetic variation. This finding highlights the importance of highways as corridors for the spread of M. micrantha in southern China.
道路作为种子或果实空间扩散的廊道，对入侵物种的定殖和扩散有重大影响，但其在种群遗传变异中的具体作用仍知之甚少。南美杂草薇甘菊自1984年引入深圳地区后，已在中国南方迅速蔓延。本研究调查了其遗传多样性如何沿公路分布，以及公路是否充当了薇甘菊快速扩张的廊道。方法：在中国南方的四条公路沿线采集了27个路边种群的样本，使用12个微卫星标记对787个样本进行了检测。对种群间的遗传多样性变异进行了量化，并分析了遗传分化模式。
在这种自交不亲和的植物中，物种和种群水平均发现了高水平的遗传多样性（预期杂合度分别为0·497和0·477；等位基因丰富度分别为2·580和2·521）。种群间的赖特F统计值（0·044，P < 0·01）以及分子方差分析（91%的遗传变异存在于种群内，9%存在于公路内的种群间，4条公路间为0%）表明种群间遗传分化水平相对较低，而主坐标分析和聚类分析也表明种群间缺乏明显的地理遗传结构。计算得出的N值为5·5，表明基因流较强。
遗传变异模式与沿公路的扩散促进作用一致。路边种群间的遗传混合意味着在定殖过程中发生了多次种群引入。与公路上车辆运输相关的种子远距离扩散可能在塑造遗传变异方面发挥了重要作用。这一发现凸显了公路作为薇甘菊在中国南方扩散廊道的重要性。
