Complete mitochondrial genomes of Lycosa grahami and Lycosa sp. (Araneae: Lycosidae): comparison within the family Lycosidae

Mitochondrial genome (mitogenome) sequencing is one of the most effective methods for studying spider phylogeny. In this study, the mitogenomes of wolf spiders (Lycosa grahami and Lycosa sp.) were sequenced and compared with those of other spiders to study their evolutionary trends. The mitogenomes of L. grahami and Lycosa sp. were 14,240 and 14,589 bp in length, respectively, and their adenine and thymine contents were 73.74% and 76.23%, respectively. The mitogenomes contained 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), two ribosomal RNAs (rRNAs), and a control region. We found that trnS1 and trnS2 of four Lycosa species lacked a dihydrouracil arm, most tRNAs lacked a T psi C arm, and there was a guanine-uracil wobble in the acceptor stem. Comparison of selective pressures on the 13 PCGs in the mitogenomes of Lycosidae showed the fastest evolution for ATP8 and the slowest for COI. Concatenated nucleotide sequences of the 13 PCGs and two rRNA genes were obtained from the mitogenomes of 63 spiders for phylogenetic analysis based on maximum likelihood and Bayesian inference methods. Phylogenetic relationships supported the monophyletic Mesothelae and Mygalomorphae. Lycosa clustered under a monophyletic group in Lycosidae. In addition, L. grahami and L. shansia were found to be more closely related to Lycosa sp. and L. singoriensis, respectively. This study provides crucial molecular information for further studies on the evolution and genetic diversity of the spider mitogenome.