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ARS Home » Plains Area » Kerrville, Texas » Knipling-Bushland U.S. Livestock Insects Research Laboratory » Cattle Fever Tick Research Unit » Research » Publications at this Location » Publication #414910
Research Project: Integrated Pest Management of Cattle Fever Ticks

Location: Cattle Fever Tick Research Unit

Title: Microsatellites and single nucleotides reveal speciation within the Amblyomma maculatum group

Author
item DEESE, HENREY - Georgia Southern University
item DE MEEUS, THEIRRY - University Of Montpellier
item LADO, PAULA - US Department Of Agriculture (USDA)
item PADDOCK, CHRISTOPHER - Centers For Disease Control And Prevention (CDC) - United States
item KENNEDY, ASHLEY - State Of Delaware Division Of Fish & Wildlife
item Maestas, Lauren

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: The Gulf Coast tick, the primary vector of Rickettsia parkeri, is found from South America to North America. In the U.S., two populations exist and slightly differ physically from each other: the population in the southwestern US and northwest Mexico (called A. maculatum morphotype III) and the population found east of the Rocky Mountains (called A. maculatum morphotype II). By analyzing and comparing 6 genetic markers and single amino acid differences in DNA, we sought to determine if these two populations are distinct species. This study is the first comparison between these two molecular markers in ticks. Genetic analysis revealed very strong genetic isolation between morphotype II and morphotype III with virtually no interbreeding between the two populations. Given this and previous studies investigating the relationship between the two morphotypes, morphotype III should be elevated to the species level under the integrative species concept. In addition, the morphotype II subpopulation from Texas displayed strong differentiation when compared to other Eastern subpopulations. Between other Eastern subpopulations there was low to moderate differentiation with no isolation by distance, indicative of dispersal primarily driven by migrating birds. The various genetic markers were equivalent in their assessment of genetic differentiation, though SNPs had much greater precision and possessed a clearer ability to cluster distinct groups by discriminate analysis of principal components.

Technical Abstract: The Gulf Coast tick (Amblyomma maculatum Koch, 1844), the primary vector of Rickettsia parkeri, is widespread from northern South America to North America. In the U.S., two populations differ morphologically from each other: the population in the southwestern US and northwest Mexico (called A. maculatum morphotype III) and the population found east of the Rocky Mountains (called A. maculatum morphotype II). By analyzing and comparing 6 microsatellite loci and single nucleotide polymorphisms (SNPs) generated from ddRADseq we further evaluated the hypothesis that these two populations are distinct species. This study is the first comparison between these two molecular markers in ticks. Both microsatellites and SNPs revealed very strong genetic isolation between morphotype II and morphotype III with virtually nonexistent gene flow between the two populations. Given this and previous studies investigating the relationship between the two morphotypes, morphotype III should be elevated to the species level under an integrative species concept. In addition, the morphotype II subpopulation from Texas displayed strong differentiation when compared to other Eastern subpopulations. Between other Eastern subpopulations there was low to moderate differentiation with no isolation by distance, indicative of dispersal primarily driven by migrating birds. Microsatellites and SNPs were equivalent in their assessment of genetic differentiation, though SNPs had much greater precision and possessed a clearer ability to cluster distinct groups by discriminate analysis of principal components.