Unravelling the evolutionary processes underlying range expansions is fundamental to understand the distribution of organisms, as well as to predict their future responses to environmental change. Predictions for range expansions include a loss of genetic diversity and an accumulation of deleterious alleles along the expansion axis, which can decrease fitness at the range‐front (expansion load). In plants, empirical studies supporting expansion load are scarce, and its effects remain to be tested outside a few model species. Leontodon longirostris is a colonizing Asteraceae with a widespread distribution in the Western Mediterranean, providing a particularly interesting system to gain insight into the factors that can enhance or mitigate expansion load. In this study, we produced a first genome draft for the species, covering 418 Mbp (~53% of the genome). Although incomplete, this draft was suitable to design a targeted sequencing of ~1.5 Mbp in 238 L. longirostris plants from 21 populations distributed along putative colonization routes in the Iberian Peninsula. Inferred demographic history supports a range expansion from southern Iberia around 40,000 years ago, reaching northern Iberia around 25,000 years ago. The expansion was accompanied by a loss of genetic diversity and a significant increase in the proportion of putatively deleterious mutations. However, levels of expansion load in L. longirostris were smaller than those found in other plant species, which can be explained, at least partially, by its high dispersal ability, the self‐incompatible mating system, and the fact that the expansion occurred along a strong environmental cline.

中文翻译：

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整个定居范围内定殖物种Leontodon longirostris（Asteraceae）的人口学，遗传多样性和扩展负荷

揭示范围扩展的进化过程对于理解生物的分布以及预测其对环境变化的未来响应至关重要。范围扩展的预测包括遗传多样性的丧失和扩展轴上有害等位基因的积累，这会降低范围前端的适应性（扩展负载）。在植物中，缺乏支持膨胀负荷的经验研究，其影响尚待少数模型物种之外的检验。鱼是一个定居的菊科，在西地中海地区广泛分布，提供了一个特别有趣的系统来深入了解可以增强或减轻扩展负荷的因素。在这项研究中，我们产生了该物种的第一个基因组草图，覆盖418 Mbp（约占基因组的53％）。尽管不完整，但该草案仍适合设计238 L中约1.5 Mbp的靶向测序。 长龙来自21个种群的植物沿着伊比利亚半岛的定居定居路线分布。推断的人口历史支持范围从大约40,000年前的伊比利亚南部扩展到大约25,000年前的伊比利亚北部。扩大伴随着遗传多样性的丧失和推定有害突变的比例显着增加。但是，L中的膨胀负荷水平。 longirostris比其他植物中的小，这至少可以部分解释为它的高分散能力，自交不亲和的交配系统以及沿着强力环境线扩展的事实。