Testing the efficiency of nested barriers to dispersal in the Mediterranean high mountain plant Edraianthus graminifolius (Campanulaceae)

Due to strong spatial heterogeneity and limited Pleistocene glaciation, the Balkan Peninsula is a major European biodiversity hotspot. Surprisingly little, however, is known about patterns and processes of intraspecific diversification of its biota in general and of high altitude species in particular. A well-suited system to test hypotheses with respect to various isolating factors acting at different geographic scales and to explore full-range phylogeographic patterns on the Balkan Peninsula is Edraianthus graminifolius (Campanulaceae), distributed in the western Balkan mountain systems, the southwestern Carpathians and the Apennine Peninsula. To this end, we used a dense population sampling and employed Amplified Fragment Length Polymorphism (AFLP) markers and plastid DNA sequences supplemented by ecological niche modelling. The strongest splits were inferred to separate southern and northern Balkan populations from the central ones, from where range extension occurred to the Carpathians and, in more recent times, once or twice to the Apennine Peninsula. The three genetic groups in the western Balkan Peninsula were remarkably congruent among molecular markers suggesting that the barriers to gene flow acted over long time periods facilitating allopatric differentiation. Each main group of Balkan populations contained genetically and geographically distinct subgroups, which likely are the result of local refugia during warmer periods. Evidently, the topographically highly complex and during the last glacial maximum only locally glaciated Balkan Peninsula is a hotspot of species richness and endemism as well as a sanctuary of intraspecific genetic diversity, even if the underlying causes remain insufficiently understood.

由于强烈的空间异质性和有限的更新世（Pleistocene）冰川作用，巴尔干半岛是欧洲主要的生物多样性热点区域。然而，学界对该区域生物类群的整体种内分化模式与过程，尤其是高海拔物种的相关研究仍极为匮乏。针对巴尔干半岛，可用于检验不同地理尺度下各类隔离因子相关假说，并探索完整谱系地理（phylogeography）格局的理想研究类群，是分布于巴尔干西部山地、喀尔巴阡山脉西南部以及亚平宁半岛的*Edraianthus graminifolius*（桔梗科Campanulaceae）。为此，本研究采用高密度种群取样策略，运用扩增片段长度多态性（Amplified Fragment Length Polymorphism, AFLP）分子标记与质体DNA序列，并辅以生态位建模开展研究。研究推断的最显著遗传分化事件，将巴尔干半岛的南部、北部种群与中部种群区分开；中部种群是向喀尔巴阡山脉进行分布范围扩张的起源地，且在更近的地质时期又1~2次扩张至亚平宁半岛。巴尔干西部的三个遗传类群在不同分子标记下表现出高度一致性，表明基因流障碍长期存在，推动了异域分化进程。巴尔干半岛的每个主要种群类群，均包含遗传与地理特征均显著分化的亚群，这大概率是暖期局部避难所作用的结果。显然，地形高度复杂且末次冰盛期（Last Glacial Maximum）仅局部被冰川覆盖的巴尔干半岛，既是物种丰富度与特有性热点区域，也是种内遗传多样性的庇护所，尽管其背后的驱动机制仍未得到充分阐释。