Maylandt Clemens, Kirschner Philipp, Pirkebner Daniela, Frajman Božo, Peñas de Giles Julio, Schönswetter Peter, Carnicero Pau
Department of Botany, University of Innsbruck, Sternwartestr. 15, 6020 Innsbruck, Austria.
Botany Department, University of Granada, 18071 Granada, Spain.
Mol Phylogenet Evol. 2025 Mar;204:108242. doi: 10.1016/j.ympev.2024.108242. Epub 2024 Nov 16.
The Eurasian steppes are among the largest and most threatened biomes on Earth. During cold periods of the Pleistocene, the zonal Eurasian steppes had a much larger extent as compared to interglacial periods, and repeatedly expanded into large areas of present-day forested temperate Europe. Conversely, during warm periods, forest expansion recurrently forced Eurasian steppe biota into disjunct and small warm-stage refugia, i.e. today's extrazonal steppes. The rare, threatened and disjunctly distributed northwestern African and European members of Astragalus sect. Caprini constitute an ideal model for gaining insights into the evolutionary dynamics of typical steppe biota. Here, we reconstructed the spatiotemporal diversification of northwestern African and European members of Astragalus sect. Caprini based on a combination of RADseq data, single gene markers (internal transcribed spacer, plastid ycf1), genome size measurements and multivariate morphometrics. We outline an evolutionary scenario in which the group originated in the Irano-Turanian region and started to diversify shortly after the Mid-Pleistocene-Transition (ca. 0.5 to 0.7 Ma). While lineages occurring in (sub-)mediterranean mountain ranges diverged early, lineages occurring in northern lowland steppes are much younger (ca. 0.2 to 0.3 Ma), emphasizing the importance of southern European mountain ranges as long-term refugia. Recurrent colonization of the western Mediterranean region by eastern Mediterranean lineages and secondary contacts of currently spatially isolated lineages have significantly (co-)shaped the genetic structure within the group; we assume that these events may be a consequence of cold-stage range expansions. Based on combined genetic and morphometric data, we suggest treating the ten lineages introduced in this study as independent species, contrasting previous taxonomic treatments.
欧亚草原是地球上面积最大且受威胁最严重的生物群落之一。在更新世的寒冷时期，与间冰期相比，欧亚地带性草原的范围要大得多，并多次扩张至现今欧洲温带森林覆盖的大片区域。相反，在温暖时期，森林扩张反复迫使欧亚草原生物群进入分散且面积较小的暖期避难所，即如今的非地带性草原。黄芪属山羊豆组中分布于西北非洲和欧洲、珍稀且受威胁的间断分布成员，是深入了解典型草原生物群进化动态的理想模型。在此，我们基于简化基因组测序（RADseq）数据、单基因标记（内转录间隔区、质体ycf1）、基因组大小测量和多变量形态测量相结合的方法，重建了黄芪属山羊豆组西北非洲和欧洲成员的时空多样化过程。我们勾勒出一个进化情景，即该类群起源于伊朗 - 图兰地区，并在中更新世过渡时期（约0.5至0.7百万年前）之后不久开始多样化。虽然出现在（亚）地中海山脉的谱系分化较早，但出现在北部低地草原的谱系则年轻得多（约0.2至0.3百万年前），这凸显了南欧山脉作为长期避难所的重要性。东地中海谱系对西地中海地区的反复殖民以及当前空间隔离谱系的二次接触，显著（共同）塑造了该类群内部的遗传结构；我们认为这些事件可能是寒冷期范围扩张的结果。基于综合的遗传和形态测量数据，我们建议将本研究中引入的十个谱系视为独立物种，这与先前的分类处理不同。
