Data from: Species biodiversity can be overestimated by a fixed empirical threshold: insights from DNA barcoding of the genus Cletus and COI data from previous phylogeographical studies

The use of genetic distances to identify species within the framework of DNA barcoding has to some extent accelerated the development of biodiversity studies. However, using a fixed empirical threshold to delimit species may lead to overestimating biodiversity. In this study we use a new data set of COI sequences for 366 specimens within the genus of Cletus, as well as conduct an analysis on the same genetic data for collected morphologically-defined species from previous phylogeographical studies, in order to test whether high intraspecific genetic differentiations are common with the premises of comprehensive sampling. The results indicated that C. punctiger (Dallas, 1852) and C. graminis Hsiao & Cheng, 1964 should be the same species, and that the distributional record of C. pugnator (Fabricius, 1787) in China should be reconsidered. High intraspecific genetic differentiations (0-4.35%) were found in C. punctiger. Furthermore, as for the mined data, the maximum intraspecific K2P distances of 186 species (48.44% of 384) exceed 3%, 101 species (26.30%) can be divided into two or more clusters with a threshold of 3% in cluster analysis. If genetic distance is used to delimit species boundaries, the minimum interspecific K2P distance of the congeneric species should be considered rather than only using the fixed empirical value; otherwise, the species number may be overestimated in some cases.