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Abstract :

Ixodes ricinus is the main vector species for pathogenic agents transmitted by ticks in Europe. A better knowledge of its genetic variability is especially useful for the design of control methods (against tick vaccine…). Through population genetics and the assessment of gene flow, it also allows to estimate tick dispersal and hence a better understanding of tickborne diseases. We have developed a new type of molecular markers (Single Nucleotide Polymorphism) by
generating by pyrosequencing a large amount of sequencing reads (643 billions of nucleotides) from the I. ricinus genome. Without any reference genome available, we have used a unique bioinformatics pipeline (DiscoSneap) to isolate 1765 SNPs. Each of 384 selected loci have been validated by the genotyping of 480 individual nymphs sampled in an area located in the north of the Bretagne region containing a 1000 hectare forest surrounded by hedges. An heterozygous
deficiency was observed, even at the finest spatial scale investigated, indicating a large inbreeding that could be due to the weak dispersal abilities of larvae and/or the existence of host races. All the population genetic analysis conducted suggest a large amount of gene flow within the whole studied area.
Those markers provide an important tool for the investigation of genetic variability in this tick, from the building of a genetic map to the identification of genes of involved in the epidemiology of tick-borne diseases.

Key words :

ticks, population genetics, single nucleotide polymorphism, NGS, bioinformatics, dispersal, inbreeding