Comparative mitochondrial genomics suggests lack of deep host-associated divergence in Pulex irritans (Arthropoda:...

The population structure of the generalist flea Pulex irritans, an important vector for zoonotic pathogens, remains poorly understood, limiting efforts to predict and control disease transmission across the human-animal-environment interface. We performed a comparative mitochondrial (mt) genomic analysis to assess for the presence of deep, host-associated genetic lineages in P. irritans. Complete mt genomes were sequenced from fleas collected from a human and a wild marmot using high-throughput sequencing, and compared with a published dog-derived mt genome from China. The newly assembled mt genomes were approximately 20.4 kb in length and exhibited high conservation, with pairwise nucleotide identities exceeding 98.7% and identical gene organization. Phylogenomic analyses placed all P. irritans isolates within a single, cohesive lineage (Bpp = 1.0; UFBoot = 100), showing no evidence of deep, host-specific substructuring. While the high genetic similarity (>98%) is expected for conspecifics, the absence of deep phylogenetic splitting challenges the hypothesis of ancient, host-specific cryptic species. Ka/Ks ratios for all 13 protein-coding genes were < 1, indicating strong purifying selection. Although limited by sample size, this study provides baseline genomic evidence suggesting that P. irritans likely does not comprise a complex of anciently diverged host-specialized lineages in this region. These findings highlight its potential as a versatile vector and emphasize the need for integrated One Health surveillance strategies.