de Dato Giovanbattista D, Teani Angela, Mattioni Claudia, Aravanopoulos Filippos, Avramidou Evangelia V, Stojnic Srdjan, Ganopoulos Ioannis, Belletti Piero, Ducci Fulvio
Research Centre for Forestry and Wood, Council for Agricultural Research and Economics, Arezzo, Italy.
Research Institute on Terrestrial Ecosystems, National Research Council, Porano, Italy.
Front Plant Sci. 2020 Mar 24;11:310. doi: 10.3389/fpls.2020.00310. eCollection 2020.
In the main distribution area the genetic pattern of silver birch is dominated by two haplotypes: haplotype A located in the western and north-western Europe, and haplotype C in eastern and southeastern Europe, characterized by high levels of neutral genetic variability within populations, and low differentiation among populations. Information about the amount and structure of genetic variation in the southern marginal areas, representing rear populations left during the expansion of this species from southern glacial refugia, are lacking. The general aim of the study was to investigate the existence of the climatic characteristics typical of the environmental niche of the species, jointly to genetic organization, variation and gene flow, in marginal populations on the Italian Apennines and Greek Southern Rhodope and compare them with populations of the southern part of the main distribution range on the Alps and Balkans. Genetic analysis was performed using nuclear microsatellites loci on 311 trees sampled from 14 populations. Environmental analysis was performed on the multivariate analysis of derived climatic variables. The allelic pattern was analyzed to assess genetic diversity, population diversity and differentiation, population structure and gene flow. The geographic and environmental peripherality did not always match, with some Apennine sites at higher elevation enveloped in the environmental niche. In the peripheral populations on the Apennines, we observed a lower genetic diversity and higher differentiation, with evident genetic barriers detected around these sites. These characteristics were not shown in the marginal Greek populations. Unexpectedly, the southern Italian marginal populations showed genetic links with the Greek and central area of the distribution range. The Greek populations also showed evident gene flow with the Alpine and Balkan areas. The disparity of results in these two marginal areas show that it is not the geographic peripherality or even the ecological marginality that may shape the genetic diversity and structure of marginal populations, but primarily their position as part of the continuous range or as disjunct populations. This outcome suggests different considerations on how to manage their gene pools and the role that these rear populations can play in maintaining the biodiversity of this species.
在主要分布区，欧洲白桦的遗传模式由两种单倍型主导：位于西欧和西北欧的单倍型A，以及位于东欧和东南欧的单倍型C，其特征是种群内中性遗传变异水平高，种群间分化低。关于该物种从南部冰川避难所扩张过程中遗留的边缘种群，即南部边缘地区遗传变异的数量和结构的信息尚缺。本研究的总体目标是调查该物种环境生态位典型气候特征的存在情况，并将其与意大利亚平宁山脉和希腊南部罗多彼山脉边缘种群的遗传组织、变异和基因流相结合，同时将这些边缘种群与阿尔卑斯山和巴尔干半岛主要分布范围南部的种群进行比较。使用核微卫星位点对从14个种群中采样的311棵树进行了遗传分析。对推导的气候变量进行多变量分析以进行环境分析。分析等位基因模式以评估遗传多样性、种群多样性和分化、种群结构和基因流。地理和环境边缘性并不总是匹配的，一些海拔较高的亚平宁地区处于环境生态位范围内。在亚平宁山脉的边缘种群中，我们观察到遗传多样性较低和分化较高，并且在这些地点周围检测到明显的遗传屏障。这些特征在希腊边缘种群中未表现出来。出乎意料的是，意大利南部边缘种群与希腊和分布范围中部地区存在遗传联系。希腊种群也与阿尔卑斯山和巴尔干地区表现出明显的基因流。这两个边缘地区结果的差异表明，塑造边缘种群遗传多样性和结构的并非地理边缘性甚至生态边缘性，而是它们作为连续分布范围一部分或间断种群的位置。这一结果提示在如何管理它们的基因库以及这些边缘种群在维持该物种生物多样性中所起的作用方面需要不同的考虑。
