Abstract
The Rhipicephalus sanguineus group encompasses at least 12 validated species of Palearctic and Afrotropical hard ticks, which are relevant in veterinary medicine and public health. The taxonomy of R. sanguineus s.s., has been particularly intensely debated, due to its wide geographic distribution, morphological variants, parasite-host associations, and its capacity and vectorial competence for the transmission of several pathogens. By sequencing mitochondrial markers, it was possible to identify the existence of multiple lineages, among which the Tropical and the Temperate lineages stand out, particularly in America. However, the northern limit between these lineages is not clear due to the lack of extensive sampling across Mexico. For this reason, the aim of the present study was to determine the genetic diversity and structure of the R. sanguineus group in Mexico and to compare it with the populations reported in the Americas, in order to propose the northern limit of the R. sanguineus Tropical lineage and the potential regions of sympatry with R. sanguineus s.s. The findings of this study now confirm the presence of R. sanguineus s.s. in Mexico, showing a subtle genetic structure and high genetic diversity throughout its distribution in the Americas. In contrast, the Tropical lineage seems to be genetically less diverse in its overall distribution in the Americas. The genetic diversity of these two independent lineages could have important epidemiological implications in the transmission of tick pathogens.
Highlights
The Rhipicephalus sanguineus group encompasses at least 12 validated species (R. camicasi, R. guilhoni, R. leporis, R. moucheti, R. pumilio, R. pusillus, R. rossicus, R. schulzei, R. sulcatus, R. turanicus, R. sanguineus, and the recently described R. afranicus) of Palearctic and/or Afrotropical hard ticks widely distributed worldwide by several historical colonization processes, which exhibit a high relevance in veterinary medicine and public health due to direct damage caused by infestation in the hosts and by the transmission of pathogens [1,2]
Within the R. sanguineus group, the phylogenetic associations were not completely resolved, since only Clade III was resolved, but the relationships among the groups formed by R. turanicus, R. guilhoni, R. camicasi, R. leporis, and the Tropical Lineage were not resolved (Supplementary File 2)
According to the phylogenetic analysis, the PCoA revealed two well-distinctive Pathogens 2021, 10, x FOR PEER REmVIoElWecular groups distributed in the Americas: the R. sanguineus s.s. and the R. s7aonfg1u5ineus s.l
Summary
The Rhipicephalus sanguineus group encompasses at least 12 validated species (R. camicasi, R. guilhoni, R. leporis, R. moucheti, R. pumilio, R. pusillus, R. rossicus, R. schulzei, R. sulcatus, R. turanicus, R. sanguineus, and the recently described R. afranicus) of Palearctic and/or Afrotropical hard ticks widely distributed worldwide by several historical colonization processes, which exhibit a high relevance in veterinary medicine and public health due to direct damage caused by infestation in the hosts and by the transmission of pathogens [1,2]. Considering the biogeographic regionalisation proposed by Morrone et al [12], and that the limit between the Nearctic and Neotropical regions occurs in Mexico, we formulated the hypothesis that the northern limits of both lineages of the R. sanguineus group must be in accordance with this biogeographic regionalisation. Several populations of both linages are well-known vectors of tick-borne pathogens such as Rickettsia rickettsii and Ehrlichia canis, which cause Rocky Mountain Spotted Fever and canine monocytic ehrlichiosis in America, respectively [9,13,14,15,16].
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