Morphological, Molecular Identification and Genetic Diversity Assessment of Three Terrestrial Isopods from the High-Altitude Region

Terrestrial specimens were collected from Ashshafa, a south-western highland area in Saudi Arabia. Three species, i.e., Porcellio laevis, Porcellionides pruinosus (Porcellionidae), and Armadillidium vulgare (Armadillidiidae), were identified in this study based on their morphological characteristics. Partial mitochondrial cytochrome C oxidase subunit I (COI) gene sequences were used for DNA barcoding and biodiversity assessments. A phylogenetic tree of 22 haplotypes from 35 specimens of the three isopod species was drawn from the most similar sequences obtained from BLAST with the associated accession numbers. The tree included two clades. The first clade included samples of P. laevis and P. pruinosus, whereas the second clade included samples of A. vulgare. Each identified species formed a distinct subclade within the main clade, along with similar sequences obtained from the NCBI database. The heat map of genetic distance among haplotypes shows the haplotype diversity (Hd) ranged from 0.590 to 0.933 (mean = 0.767) and total nucleotide diversity (πT) ranged from 0.001 to 0.089 (mean=0.049), with a similar trend observed for nucleotide diversity per site (θw) ranged from 0.001 to 0.80 (mean = 0.049). In contrast, synonymous nucleotide diversity (πs), mean=0.009, was low compared to nonsynonymous nucleotide diversity (πs), mean=0.060, across all species. In conclusion, the morphological identification of terrestrial isopods was confirmed using COI gene sequencing of mitochondrial DNA. These results will be helpful in developing a deeper isopod identification method.