Centre for Forest Conservation Genetics and Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, British Columbia.
Am J Bot. 2013 Aug;100(8):1651-62. doi: 10.3732/ajb.1200654. Epub 2013 Aug 8.
Historic colonization and contemporary evolutionary processes contribute to patterns of genetic variation and differentiation among populations. However, separating the respective influences of these processes remains a challenge, particularly for natural hybrid zones, where standing genetic variation may result from evolutionary processes both preceding and following contact, influencing the evolutionary trajectory of hybrid populations. Where adaptation to novel environments may be facilitated by interspecific hybridization, teasing apart these processes will have practical implications for forest management in changing environments.
We evaluated the neutral genetic architecture of the Picea sitchensis (Sitka spruce) × P. glauca (white spruce) hybrid zone along the Nass and Skeena river valleys in northwestern British Columbia using chloroplast, mitochondrial, and nuclear microsatellite markers, in combination with cone morphological traits.
Sitka spruce mitotype "capture", evidenced by this species dominating the maternal lineage, is consistent with earlier colonization of the region by Sitka spruce. This "capture" differs from the spatial distribution of chloroplast haplotypes, indicating pollen dispersal and its contribution to geographic structure. Genetic ancestry, based on nuclear markers, was strongly influenced by climate and geography. Highly parallel results for replicate transects along environmental gradients provide support for the bounded hybrid superiority model of hybrid zone maintenance. •
This broad-scale analysis of neutral genetic structure indicates the importance of historic and contemporary gene flow, environmental selection, and their interaction in shaping neutral genetic variation within this hybrid zone, informative to seed transfer development and reforestation for future climates.
历史殖民和当代进化过程促成了种群间遗传变异和分化的模式。然而，要分离这些过程的各自影响仍然是一个挑战，特别是对于自然杂交区，其中的遗传变异可能是由于接触前后的进化过程而产生的，影响了杂交种群的进化轨迹。如果适应新环境的能力可以通过种间杂交来促进，那么将这些过程分开将对变化环境中的森林管理具有实际意义。
我们使用叶绿体、线粒体和核微卫星标记，结合锥体形态特征，评估了不列颠哥伦比亚省西北部 Nass 和 Skeena 河谷的 Picea sitchensis（Sitka 云杉）× P. glauca（白云杉）杂交区的中性遗传结构。
该物种主导母系谱系的 Sitka 云杉的 mitotype“捕获”，证明了 Sitka 云杉对该地区的早期殖民。这种“捕获”与叶绿体单倍型的空间分布不同，表明花粉传播及其对地理结构的贡献。基于核标记的遗传祖先受气候和地理的强烈影响。在环境梯度上沿重复横断面的高度平行结果为杂交区维持的有界杂种优势模型提供了支持。
对中性遗传结构的广泛分析表明，历史和当代基因流、环境选择及其相互作用在塑造该杂交区中性遗传变异方面的重要性，这对未来气候下的种子转移发展和重新造林具有信息意义。
