Data from: Mitochondrial lineage sorting in action – historical biogeography of the Hyles euphorbiae complex (Sphingidae, Lepidoptera) in Italy

Background: Mitochondrial genes are among the most commonly used markers in studies of species’ phylogeography and to draw conclusions about taxonomy. The Hyles euphorbiae complex (HEC) comprises six distinct mitochondrial lineages in the Mediterranean region, of which one exhibits a cryptic disjunct distribution. The predominant mitochondrial lineage in most of Europe, euphorbiae, is also present on Malta; however, it is nowadays strangely absent from Southern Italy and Sicily, where it is replaced by 'italica'. A separate biological entity in Italy is further corroborated by larval colour patterns with a congruent, confined suture zone along the Northern Apennines. By means of historic DNA extracted from museum specimens, we aimed to investigate the evolution of the mitochondrial demographic structure of the HEC in Italy and Malta throughout the Twentieth Century. Results: At the beginning of the Twentieth Century, the European mainland lineages were also present at a moderate frequency in Southern Italy and Sicily. The proportion of 'italica' then steadily increased in this area from below 60 percent to near fixation in about 120 years. Thus, geographical sorting of mitochondrial lineages in the HEC was not as complete then as the current demography suggests. The pattern of an integral 'italica' core region and a disjunct euphorbiae distribution evolved very recently. To explain these strong demographic changes, we propose genetic drift due to anthropogenic habitat loss and fragmentation in combination with an impact from recent climate warming that favoured the spreading of the potentially better adapted 'italica' populations. Conclusions: The pattern of geographically separated mitochondrial lineages is commonly interpreted as representing long term separated entities. However, our results indicate that such a pattern can emerge surprisingly quickly, even in a widespread and rather common taxon. We thus caution against drawing hasty taxonomic conclusions from biogeographical patterns of mitochondrial markers derived from modern sampling alone.

背景：线粒体基因是物种系统地理学研究以及分类学推断中最常用的分子标记之一。大戟天蛾复合群（Hyles euphorbiae complex, HEC）在地中海区域分布有6个独立的线粒体谱系，其中1个谱系呈现隐秘的间断分布格局。欧洲大部分地区的优势线粒体谱系euphorbiae同样分布于马耳他；但如今该谱系却离奇地从意大利南部与西西里岛消失，被"italica"谱系所取代。意大利境内存在独立生物学类群这一结论，进一步得到幼虫体色模式的佐证——其沿北亚平宁山脉分布有一致且局限的缝合带特征。本研究借助从博物馆标本中提取的历史DNA，旨在探究20世纪期间意大利与马耳他境内HEC的线粒体种群结构演化历程。
结果：20世纪初期，意大利南部与西西里岛也曾以中等频率分布有欧洲大陆谱系。在此后的约120年间，该区域内"italica"谱系的占比从不足60%稳步攀升至近乎固定。由此可见，当时HEC线粒体谱系的地理分异并未如当前种群结构所呈现的那般彻底。"italica"核心分布区与euphorbiae间断分布的格局是在极晚近的时期才形成的。针对上述剧烈的种群结构变化，我们提出以下解释：人类活动导致的栖息地丧失与片段化引发的遗传漂变，叠加近期气候变暖对适应性更强的"italica"种群扩散的促进作用。
结论：地理分隔的线粒体谱系格局通常被解读为长期演化隔离的类群特征。但本研究结果表明，这类格局可以出乎意料地快速形成，即便在广布且常见的类群中亦是如此。因此，我们提醒研究者不应仅基于现代采样得到的线粒体标记生物地理格局，就仓促做出分类学推断。