Gaytán Álvaro, Bergsten Johannes, Canelo Tara, Pérez-Izquierdo Carlos, Santoro Maria, Bonal Raul
Department of Ecology Environment and Plant Sciences Stockholm University Stockholm Sweden.
Research Group on Genetic and Cultural Biodiversity - IREC - (CSIC, UCLM, JCCM) Ciudad Real Spain.
Ecol Evol. 2020 Sep 1;10(19):10754-10772. doi: 10.1002/ece3.6733. eCollection 2020 Oct.
DNA barcoding identification needs a good characterization of intraspecific genetic divergence to establish the limits between species. Yet, the number of barcodes per species is many times low and geographically restricted. A poor coverage of the species distribution range may hamper identification, especially when undersampled areas host genetically distinct lineages. If so, the genetic distance between some query sequences and reference barcodes may exceed the maximum intraspecific threshold for unequivocal species assignation. Taking a group of herbivores (moths) in Europe as model system, we found that the number of DNA barcodes from southern Europe is proportionally very low in the Barcoding of Life Data Systems. This geographical bias complicates the identification of southern query sequences, due to their high intraspecific genetic distance with respect to barcodes from higher latitudes. Pairwise intraspecific genetic divergence increased along with spatial distance, but was higher when at least one of the sampling sites was in southern Europe. Accordingly, GMYC (General Mixed Yule Coalescent) single-threshold model retrieved clusters constituted exclusively by Iberian haplotypes, some of which could correspond to cryptic species. The number of putative species retrieved was more reliable than that of multiple-threshold GMYC but very similar to results from ABGD and jMOTU. Our results support GMYC as a key resource for species delimitation within poorly inventoried biogeographic regions in Europe, where historical factors (e.g., glaciations) have promoted genetic diversity and singularity. Future European DNA barcoding initiatives should be preferentially performed along latitudinal gradients, with special focus on southern peninsulas.
DNA条形码识别需要很好地描述种内遗传分化，以确定物种之间的界限。然而，每个物种的条形码数量往往很低，而且在地理上受到限制。物种分布范围的覆盖不足可能会妨碍识别，特别是当采样不足的地区存在遗传上不同的谱系时。如果是这样，一些查询序列与参考条形码之间的遗传距离可能会超过明确物种分配的最大种内阈值。以欧洲的一组食草动物（蛾类）为模型系统，我们发现，在生命条形码数据系统中，来自南欧的DNA条形码数量相对非常少。这种地理偏差使得南欧查询序列的识别变得复杂，因为它们与来自高纬度地区的条形码相比，种内遗传距离较高。成对种内遗传分化随着空间距离的增加而增加，但当至少一个采样地点在南欧时，分化更高。因此，GMYC（通用混合尤尔合并）单阈值模型检索到的聚类完全由伊比利亚单倍型组成，其中一些可能对应于隐存物种。检索到的假定物种数量比多阈值GMYC更可靠，但与ABGD和jMOTU的结果非常相似。我们的结果支持GMYC作为欧洲生物地理区域物种界定的关键资源，在这些区域，历史因素（如冰川作用）促进了遗传多样性和独特性。未来欧洲的DNA条形码计划应优先沿着纬度梯度进行，特别关注南部半岛。
