Molecular phylogenetic analyses indicate that the Ixodes ricinus complex is a paraphyletic group

Area of Science:

• * Molecular Phylogenetics
• * Medical Entomology
• * Parasitology

Background:

• * The Ixodes ricinus species complex is globally distributed and transmits Lyme borreliosis spirochetes.
• * It was hypothesized that this complex is monophyletic, implying a single evolutionary origin for vector competence.
• * Understanding the evolutionary history of Lyme disease vectors is crucial for disease control strategies.

Purpose of the Study:

• * To investigate the phylogenetic relationships within the Ixodes ricinus species complex.
• * To test the hypothesis that Lyme disease vector ticks form a monophyletic group.
• * To determine the evolutionary origins of vector competence for Lyme borreliosis agents.

Main Methods:

• * Molecular phylogenetic analysis using Bayesian methodology.
• * Sequencing of two fragments of mitochondrial 16S ribosomal deoxyribonucleic acid.
• * Analysis included 11 species from the I. ricinus complex and 16 additional Ixodes species.

Main Results:

• * Phylogenetic analysis indicated the Ixodes ricinus complex is not monophyletic unless three additional Ixodes species are included.
• * Major global vectors of Lyme disease agents were not found to be sister taxa.
• * The data suggest that the ability to transmit borreliosis agents has multiple evolutionary origins within Ixodes ticks.

Conclusions:

• * The Ixodes ricinus species complex is polyphyletic, challenging previous hypotheses.
• * Vector competence for Lyme disease agents likely evolved independently multiple times across different Ixodes species.
• * This finding has significant implications for understanding Lyme disease epidemiology and vector control efforts.