Low Genetic Diversity of the Only Clade of the Tick Rhipicephalus microplus in the Neotropics

DÍAZ-SÁNCHEZ, SANDRA; HERNÁNDEZ-TRIANA, LUIS M.; LABRUNA, MARCELO B.; MERINO, OCTAVIO; MOSQUEDA, JUAN; NAVA, SANTIAGO; SZABÓ, MATIAS; TARRAGONA, EVELINA; VENZAL, JOSÉ M.; DE LA FUENTE, JOSÉ; ESTRADA-PEÑA, AGUSTÍN

Pathogens

MDPI

Lugar: Berna; Año: 2023 vol. 12

This study addresses the variability of the mitochondrial cytochrome oxidase subunit I (COI)and 16S rDNA (16S), and nuclear internal transcriber spacer ITS2 (ITS2) genes in a set of field-collectedsamples of the cattle tick, Rhipicephalus microplus (Canestrini, 1888), and in geo-referenced sequencesobtained from GenBank. Since the tick is currently considered to be a complex of cryptic taxa in severalregions of the world, the main aims of the study are (i) to provide evidence of the clades of the tickpresent in the Neotropics, (ii) to explore if there is an effect of climate traits on the divergence rates ofthe target genes, and (iii) to check for a relationship between geographical and genetic distance amongpopulations (the closest, the most similar, meaning for slow spread). We included published sequencesof Rhipicephalus annulatus (Nearctic, Afrotropical, and Mediterranean) and R. microplus (Afrotropical,Indomalayan) to fully characterize the Neotropical populations (total: 74 16S, 44 COI, and 49 ITS2sequences included in the analysis). Only the clade A of R. microplus spread in the Nearctic–Neotropics.Both the K and Lambda’s statistics, two measures of phylogenetic signal, support low divergence ratesof the tested genes in populations of R. microplus in the Neotropics. These tests demonstrate that geneticdiversity of the continental populations does not correlate either with the geographic distance amongsamples or with environmental variables. The low variability of these genes may be due to a combinationof factors like (i) the recent introduction of the tick in the Neotropics, (ii) a large, effective, and fastexchange of populations, and (iii) a low effect of climate on the evolution rates of the target genes. Theseresults have implications for the ecological studies and control of cattle tick infestations