New Mitogenomes of Two Chinese Stag Beetles (Coleoptera, Lucanidae) and Their Implications for Systematics

Although conspicuous and well-studied, stag beetles have been slow to join the genomic era. In this study, mitochondrial genomes of two stag beetles, Sinodendron yunnanense and Prosopocoilus confucius, are sequenced for the first time. Both of their genomes consisted of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), 2 ribosomal RNAs (rRNAs), and a control region. The mitogenome of S. yunnanense was 16,921 bp in length, and P. confucius was 16,951 bp. The location of the gene trnL(UUR), between the A + T-rich and control region in S. yunnanense, is the first observed in Lucanidae. In P. confucius, an unexpected noncoding region of 580 bp was discovered. Maximum likelihood and Bayesian inference on the 13 mitochondrial PCGs were used to infer the phylogenetic relationships among 12 representative stag beetles and three scarab beetles. The topology of the two phylogenetic trees was almost identical: S. yunnanense was recovered as the most basal Lucanid, and the genus Prosopocoilus was polyphyletic due to P. gracilis being recovered sister to the genera Dorcus and Hemisodorcus. The phylogenetic results, genetic distances and mitogenomic characteristics call into question the cohesion of the genus Prosopocoilus. The genetic resources and findings herein attempts to redress understudied systematics and mitogenomics of the stag beetles.