Phylogenetic Lineages and Postglacial Dispersal Dynamics Characterize the Genetic Structure of the Tick, Ixodes ricinus, in Northwest Europe

Abstract

Dispersal and gene flow are important mechanisms affecting the dynamics of vectors and their pathogens. Here, patterns of genetic diversity were analyzed in many North European populations of the tick, Ixodes ricinus. Population sites were selected within and between areas separated by geographical barriers in order to evaluate the importance of tick transportation by birds in producing genetic connectivity across open sea and mountain ranges. The phylogenetic analyses of the mitochondrial control region and the cytochrome b gene revealed two distinct clades with supported sub-clades, with three genetic lineages: GB and WNo associated with Great Britain and western Norway respectively, and Eu with a wider distribution across continental Europe in agreement with much lower efficiency of tick dispersal by birds than by large mammals. The results suggest different ancestry of I. ricinus colonizing Britain and the rest of northern Europe, possibly from different glacial refuges, while ticks from western Norway and continental Europe share a more recent common ancestry. Demographic history modeling suggests a period of strong increase in tick abundance coincident with progression of the European Neolithic culture, long after their post-glacial colonization of NW Europe.

Geographical distribution and prevalence of tick‐borne encephalitis virus in questing Ixodes ricinus ticks and phylogeographic structure of the Ixodes ricinus vector in Norway

“…Our result also stands in contrast to Roed, Kvie, Hasle, Gilbert, and Leinaas (2016) who found two distinct clades with supported subclades and three genetic lineages associated with Great Britain, western Norway and a European clade with a wider distribution across continental Europe. However, Roed et al (2016) based their study on phylogegraphic analyses of the single genes; mitochondrial control region and the cytochrome b gene, instead of complete mtDNA as in our present work.…”

Perpetuation of Borreliae

“…Population genetics analyses demonstrated little population structure for I.ricinus across northern and central Europe (Meeûs et al, 2002). Some isolated populations may be distinguishable (e.g., Great Britain from Latvia and Western Norway (Dinnis et al, 2014;Røed et al, 2016). Although the English Channel is a physical barrier to tick movement, birds may easily transport ticks great distances and, thus, the low degree of apparent divergence was not expected.…”

How general are generalist parasites? The small mammal part of the Lyme disease transmission cycle in two ecosystems in northern Europe

“…The common shrew accounted for 79.1% in the west and 38.8% in the east, while the bank vole accounted for 9% in the west and 47.5% in the east for this subset of the 3 main species. Eastern and western Norway have different mitochondrial genotypes of I. ricinus ticks, suggesting a 5000-year-old difference (Røed et al 2016). There has thus been time for local host race formation.…”