Many continental species distributed in the Eurasian steppe occur as relict populations in the mountains of Western Europe. Their biogeographical responses to Quaternary climate changes have been poorly studied; however, they could have responded as cold-adapted species. We investigated the biogeographic history of a steppe beetle, Hycleus polymorphus, using mitochondrial and nuclear DNA sequences (COI, CAD, ITS2), and species distribution modelling (SDM) under present and past bioclimatic envelopes. We first performed a phylogenetic assessment to define species boundaries within the H. polymorphus species group. Specimens previously treated as Hycleus humerosus on morphological grounds are assigned to H. polymorphus, and those identified as Hycleus zebraeus assigned to Hycleus atratus. ITS2 data analyses revealed a strong phylogeographical structure of H. polymorphus populations, with four haplogroups corresponding to the (i) Italian Alps, (ii) French Alps and Pyrenees, (iii) South Balkan and Pontic mountains, and (iv) North Dinaric Alps. Based on these analyses and the SDM, we propose that during a glacial period, following the spread of steppic habitat, H. polymorphus underwent a range expansion from Asia to South-West Europe. Within the Mediterranean area, during the last interglacial the climatic suitability for the species was limited to mountains that acted as refugia and prompted allopatric divergence into four main lineages.

中文翻译：

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草原物种多形Hycleus polymorphus（鞘翅目：Meloidae：Mylabrini）的系统发育学和种群结构揭示了地中海山脉的多重避难所

分布在欧亚草原上的许多大陆物种是西欧山区的遗留种群。他们对第四纪气候变化的生物地理反应研究很少。但是，它们本可以作为适应寒冷的物种做出反应。我们调查了线虫和核DNA序列（COI，CAD，ITS2）和物种分布模型（SDM）在当前和过去的生物气候条件下的草原甲虫Hymorphus polymorphus的生物地理历史。我们首先进行了系统发育评估，以定义多形汉逊酵母物种组内的物种边界。以前根据形态学原因被视为Hycleus humerosus的标本分配给多形H.，而那些确定为Hycleus zebraeus分配给Hycleus atratus。ITS2数据分析揭示了多形汉逊酵母种群的强系统地理结构，具有四个单倍群，分别对应于（i）意大利阿尔卑斯山，（ii）法国阿尔卑斯山和比利牛斯山脉，（iii）南巴尔干和蓬蒂克山以及（iv）北狄那里克阿尔卑斯山。基于这些分析和SDM，我们建议在一个冰川时期，以下steppic栖息地蔓延，H.多型从亚洲扩展到西南欧。在地中海地区，在最后一次间冰期之间，该物种的气候适应性仅限于充当避难所并促使异源性分化成四个主要谱系的山脉。