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

Sandra Díaz-Sánchez; Luis M Hernández-Triana; Marcelo B Labruna; Octavio Merino; Juan Mosqueda; Santiago Nava; Matias Szabó; Evelina Tarragona; José M Venzal; José de la Fuente; Agustín Estrada-Peña

doi:10.3390/pathogens12111344

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

Pathogens. 2023 Nov 13;12(11):1344. doi: 10.3390/pathogens12111344.

Authors

Affiliations

¹ SaBio, Instituto de Investigación en Recursos Cinegéticos IREC-CSIC-UCLM-JCCM, Ronda de Toledo s/n, 13005 Ciudad Real, Spain.
² Animal and Plant Health Agency, Virology Department, Surrey KT15 3NB, UK.
³ Faculty of Veterinary Medicine, São Paulo 05508-270, SP, Brazil.
⁴ Faculty of Veterinary Medicine, Universidad Autónoma de Tamaulipas, Tamaulipas 87000, Mexico.
⁵ Laboratory for Research on Immunology and Vaccines, Facultad de Veterinaria, Querétaro 76230, Mexico.
⁶ IDICAL (INTA-CONICET), Instituto Nacional de Tecnología Agropecuaria (INTA), E.E.A. Rafaela, Rafaela 2300, Santa Fe, Argentina.
⁷ Hospital Veterinário, Universidade Federal de Uberlândia, Uberlândia 38405-314, MG, Brazil.
⁸ Departamento de Ciencias Biológicas, CENUR Litoral Norte, Universidad de la República, Salto 50000, Uruguay.
⁹ Department of Veterinary Pathobiology, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078, USA.
¹⁰ Department of Animal Health, Faculty of Veterinary Medicine, 50009 Zaragoza, Spain.
¹¹ Group of Research on Emerging Zoonoses, Instituto Agroalimentario de Aragón (IA2), 50013 Zaragoza, Spain.

Abstract

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-collected samples of the cattle tick, Rhipicephalus microplus (Canestrini, 1888), and in geo-referenced sequences obtained from GenBank. Since the tick is currently considered to be a complex of cryptic taxa in several regions of the world, the main aims of the study are (i) to provide evidence of the clades of the tick present in the Neotropics, (ii) to explore if there is an effect of climate traits on the divergence rates of the target genes, and (iii) to check for a relationship between geographical and genetic distance among populations (the closest, the most similar, meaning for slow spread). We included published sequences of Rhipicephalus annulatus (Nearctic, Afrotropical, and Mediterranean) and R. microplus (Afrotropical, Indomalayan) to fully characterize the Neotropical populations (total: 74 16S, 44 COI, and 49 ITS2 sequences 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 rates of the tested genes in populations of R. microplus in the Neotropics. These tests demonstrate that genetic diversity of the continental populations does not correlate either with the geographic distance among samples or with environmental variables. The low variability of these genes may be due to a combination of factors like (i) the recent introduction of the tick in the Neotropics, (ii) a large, effective, and fast exchange of populations, and (iii) a low effect of climate on the evolution rates of the target genes. These results have implications for the ecological studies and control of cattle tick infestations.

Keywords: 16S rDNA; COI; ITS-2; Neotropics; Rhipicephalus microplus; clade A; climate traits; evolution rates.

Grants and funding

The meetings of the co-authors for the preparation of the manuscript were facilitated by CYTED (“Ciencia y Tecnología en Desarrollo”) supported by the Government of Spain as “LaGar network” with contract number 118RT0542. Each co-author obtained regional or national funds for field surveys, support of laboratory colonies, and DNA extraction and processing.