title: Mitogenomes reveal diversity of the European Lyme borreliosis vector Ixodes ricinus in Italy.
abstract: In Europe, the Ixodes ricinus tick is the most important vector of the etiological agents of Lyme borreliosis and several other emerging tick-borne diseases. Because tick-borne pathogens are dependent on their vectors for transmission, understanding the vector population structure is crucial to inform public health research of pathogen dynamics and spread. However, the population structure and dynamics of this important vector species are not well understood as most genetic studies utilize short mitochondrial and nuclear sequences with little diversity. Herein we obtained and analyzed complete mitochondrial genome (hereafter "mitogenome") sequences to better understand the genetic diversity and the population structure of I. ricinus from two long-standing tick-borne disease foci in northern Italy. Complete mitogenomes of 23 I. ricinus ticks were sequenced at high coverage. Out of 23 mitogenome sequences we identified 17 unique haplotypes composed of 244 segregating sites. Phylogenetic reconstruction using 18 complete mitogenome sequences revealed the coexistence of four highly divergent I. ricinus maternal lineages despite the narrow spatial scale over which these samples were obtained (100km). Notably, the estimated coalescence time of the 18 mitogenome haplotypes is ∼427 thousand years ago (95% HPD 330, 540). This divergence between I. ricinus lineages is consistent with the mitochondrial diversity of other arthropod vector species and indicates that long-term I. ricinus populations may have been less structured and larger than previously thought. Thus, this study suggests that a rapid and accurate retrieval of full mitochondrial genomes from this disease vector enables fine-resolution studies of tick intraspecies genetic relationships, population differentiation, and demographic history.
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA; Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige (TN), Italy. Electronic address: gcarpi1@jhu.edu.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Carpi
authors.affiliation: Department of Anthropology, University of Iowa, Iowa City, IA, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kitchen
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA; Center for Comparative Genomics and Bioinformatics, Pennsylvania State University, University Park, PA, USA; Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore.
authors.forename: Hie Lim
authors.initials: HL
authors.lastname: Kim
authors.affiliation: Center for Comparative Genomics and Bioinformatics, Pennsylvania State University, University Park, PA, USA; Department of Public Health Sciences and Center for Public Health Genomics, University of Virginia, Charlottesville 22908, VA, USA.
authors.forename: Aakrosh
authors.initials: A
authors.lastname: Ratan
authors.affiliation: Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore.
authors.forename: Daniela I
authors.initials: DI
authors.lastname: Drautz-Moses
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: McGraw
authors.affiliation: Institute of Zoology, Slovak Academy of Sciences, Dubravska Cesta 9, Bratislava, Slovakia.
authors.forename: Maria
authors.initials: M
authors.lastname: Kazimirova
authors.affiliation: Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige (TN), Italy.
authors.forename: Annapaola
authors.initials: A
authors.lastname: Rizzoli
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA; Center for Comparative Genomics and Bioinformatics, Pennsylvania State University, University Park, PA, USA; Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore.
authors.forename: Stephan C
authors.initials: SC
authors.lastname: Schuster
mesh_terms: D000818:Animals; D004247:DNA / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D014644:Genetic Variation; D054629:Genome, Mitochondrial; D007303:Insect Vectors / Q000382:microbiology; D007558:Italy; D018884:Ixodes / Q000145:classification* / Q000235:genetics; D008193:Lyme Disease / Q000382:microbiology / Q000473:pathology; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D004247:DNA
keywords: Coalescent; Genetic diversity; Ixodes; Mitochondrial DNA; Phylogeography