Salticidae is the most species-rich family of spiders with diverse morphology, ecology and behavior. However, the characteristics of the mitogenomes within this group are poorly understood with relatively few well-characterized complete mitochondrial genomes. In this study, we provide completely annotated mitogenomes for Corythalia opima and Parabathippus shelfordi, which represent the first complete mitogenomes of the tribe Euophryini of Salticidae. The features and characteristics of the mitochondrial genomes are elucidated for Salticidae by thoroughly comparing the known well-characterized mitogenomes. The gene rearrangement between trnL2 and trnN was found in two jumping spider species, Corythalia opima and Heliophanus lineiventris Simon, 1868. Additionally, the rearrangement of nad1 to between trnE and trnF found in Asemonea sichuanensis Song & Chai, 1992 is the first protein-coding gene rearrangement in Salticidae, which may have an important phylogenetic implication for the family. Tandem repeats of various copy numbers and lengths were discovered in three jumping spider species. The codon usage analyses showed that the evolution of codon usage bias in salticid mitogenomes was affected by both selection and mutational pressure, but selection may have played a more important role. The phylogenetic analyses provided insight into the taxonomy of Colopsus longipalpis (Żabka, 1985). The data presented in this study will improve our understanding of the evolution of mitochondrial genomes within Salticidae.

Spiders are an extraordinary animal group with extremely high diversity in species, morphology, and behavior. Accurate estimation of species diversity and community composition is essential in spider ecological studies as well as applications of biodiversity surveys and monitoring. However, spider biodiversity surveys still largely utilize the morphology-based approach, which is often time-consuming and highly dependent on taxonomic experts. In this study, we tested the applicability of mitochondrial metagenomic and metabarcoding methods in the biodiversity survey of spiders. Local mitogenome and barcode databases of 62 reference species were built using next-generation sequencing and Sanger sequencing technologies. The performances of mitochondrial metagenomics, metabarcoding, and morphological methods were compared for five plot samples of spiders. The results show that the molecular methods (mitochondrial metagenomics and metabarcoding) have a higher species detection rate compared with the traditional morphological biodiversity method, which is largely due to their capability of incorporating the large proportion of immature specimens in each plot into the biodiversity assessment. Our study demonstrates the great potential of molecular approaches in advancing spider biodiversity and community ecology studies and suggests that by combining both mitochondrial metagenomic and metabarcoding methods we could provide more accurate and reliable biodiversity assessment for spiders.