Mitochondrial Phylogenomics yields Strongly Supported Hypotheses for Ascaridomorph Nematodes

Area of Science:

• Zoology
• Parasitology
• Genomics

Background:

• Ascaridomorph nematodes pose significant global health, veterinary, and economic challenges.
• Previous phylogenetic studies often relied on limited single-locus data, particularly nuclear ribosomal RNA, hindering accurate species identification and relationship mapping.
• Nuclear ribosomal RNA data often lacks resolution for deep evolutionary relationships.

Purpose of the Study:

• To investigate the phylogenetic relationships and taxonomic status of ascaridomorph nematodes using mitochondrial (mt) genome data.
• To resolve ambiguities in the phylogeny of ascaridomorphs, particularly concerning cryptic species.
• To provide a more robust phylogenetic framework compared to single-locus analyses.

Main Methods:

• Analysis of mitochondrial (mt) genomes from anisakids and other ascaridomorphs sourced from fish hosts globally and the GenBank database.
• Sequencing and comparative analysis of mt genomes, ranging from 13,948-14,019 bp, encoding 12 protein-coding genes, 2 ribosomal RNAs, and 22 transfer RNA genes.
• Phylogenetic reconstruction using comprehensive mt genome data to infer evolutionary relationships.

Main Results:

• Identified at least six cryptic species within the Pseudoterranova decipiens complex.
• Mitochondrial genome data did not support the hypothesis of cryptic species within Contracaecum ogmorhini.
• Confirmed the monophyly of several ascaridomorph superfamilies and families, with the exception of Ascaridiidae, aligning with previous nuclear rRNA findings.

Conclusions:

• Mitochondrial genome analysis offers a powerful approach to resolve ascaridomorph nematode phylogeny and taxonomy.
• The study highlights the presence of cryptic diversity within the Pseudoterranova decipiens complex, necessitating revised taxonomic and management strategies.
• This research provides a more resolved phylogenetic framework for ascaridomorph nematodes, advancing our understanding of their evolutionary history.