Artemisia herba-alba is an important component of Mediterranean dry steppe floras, being widely distributed in arid areas of the Iberian Peninsula and North-West Africa. In this study, we use genetic, cytogenetic and niche modelling tools to investigate the natural history of the species, focusing particularly on the role played by polyploidization to explain current diversity patterns throughout the main distribution range of the plant. Our sequencing data indicate a complex phylogeographical structure showing similar haplotype diversity patterns on both sides of the Strait of Gibraltar and no clear signals of genetic refugia. According to our cytogeographical results, we inferred multiple polyploidization events, which probably took place on the Iberian Peninsula and in North Africa independently. Environmental niche modelling suggested stable potential distributions of A. herba-alba on both sides of the Mediterranean Sea under present and past Last Glacial Maximum conditions, which could be related to the intricate spatial genetic and cytogenetic patterns shown by the species. Finally, environmental modelling comparison among cytotypes revealed that the niche of tetraploids is narrower and nested in that of diploids, a result that could indicate environmental specialization and could potentially explain recurrent establishment success of tetraploids.

中文翻译：

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伊比利亚半岛和北非的艾蒿（菊科）的植物志和细胞地理史：地中海两岸错综复杂的镜像

茵陈蒿是地中海干草原植物区系的重要组成部分，广泛分布在伊比利亚半岛和西北非洲的干旱地区。在这项研究中，我们使用遗传，细胞遗传和生态位建模工具来研究物种的自然历史，特别关注多倍体化在解释植物主要分布范围内当前多样性模式方面所起的作用。我们的测序数据表明，复杂的植物地理结构在直布罗陀海峡两岸显示相似的单倍型多样性模式，并且没有明确的遗传避难所信号。根据我们的细胞地理学结果，我们推断出了多个多倍体化事件，这些事件可能分别在伊比利亚半岛和北非发生。在当前和过去的最后冰河最大条件下，地中海两岸的拟南芥（A. herba-alba）可能与该物种显示的复杂的空间遗传和细胞遗传学模式有关。最后，细胞类型之间的环境建模比较表明，四倍体的生态位较狭窄且嵌套在二倍体中，这一结果可能表明环境专业化，并可能解释四倍体的复发建立成功。