Data from: Impact of past climatic changes and resource availability on the population demography of three food-specialist bees

Past climate change is known to have strongly impacted current patterns of genetic variation of animals and plants in Europe. However, ecological factors also have the potential to influence demographic history, and thus patterns of genetic variation. In this study, we investigated the impact of past climate, and also the potential impact of host plant species abundance, on intraspecific genetic variation in three co-distributed and related specialized solitary bees of the genus Melitta with very similar life history traits and dispersal capacities. We sequenced five independent loci in samples collected from the three species. Our analyses revealed that the species associated with the most abundant host plant species (Melitta leporina) displays unusually high genetic variation, to an extent that is seldom reported in phylogeographic studies of animals and plants. This suggests a potential role of food resource abundance in determining current patterns of genetic variation in specialized herbivorous insects. Patterns of genetic variation in the two other species indicated lower overall levels of diversity, and that M. nigricans could have experienced a recent range expansion. Ecological niche modelling of the three Melitta species and their main host plant species suggested a strong reduction in range size during the last glacial maximum. Comparing observed sequence data with data simulated using spatially explicit models of coalescence suggests that M. leporina recovered a range and population size close to their current levels at the end of the last glaciation, and confirms recent range expansion as the most likely scenario for M. nigricans. Overall, this study illustrates that both demographic history and ecological factors may have contributed to shape current phylogeographic patterns.

众所周知，过去的气候变化已强烈影响欧洲动植物当前的遗传变异格局。然而，生态因子同样可对种群历史产生作用，进而塑造遗传变异模式。本研究针对3种同分布且亲缘关系相近的专性独居蜂（Melitta属）展开探究，这类蜂类具备高度相似的生活史特征与扩散能力；我们同时考察了过去气候以及寄主植物物种丰度对其种内遗传变异（intraspecific genetic variation）的影响。我们对从这3个物种中采集的样本的5个独立基因座进行了测序。分析结果显示，与丰度最高的寄主植物共生的蜂种（Melitta leporina）表现出异常高的遗传变异水平，这种变异程度在动植物的系统地理（phylogeographic）研究中鲜有报道。这表明食物资源丰度可能在决定专植食性昆虫当前的遗传变异格局中发挥潜在作用。另外两个物种的遗传变异格局则整体呈现较低的多样性水平，且M. nigricans可能经历了近期的分布范围扩张。对这3种Melitta蜂类及其主要寄主植物的生态位建模（ecological niche modelling）结果显示，在末次盛冰期（last glacial maximum）期间，它们的分布范围大幅缩减。将观测到的序列数据与基于空间显式溯祖（coalescence）模型模拟得到的数据进行对比后发现，M. leporina在末次冰期结束后恢复至接近当前水平的分布范围与种群规模，同时证实了分布范围扩张是M. nigricans最可能的演化场景。总体而言，本研究表明，种群历史与生态因子二者均可能参与塑造当前的系统地理格局。