Molecular ecology

1365-294X33152024AugMolecular ecologyMol EcolGenome resequencing reveals population divergence and local adaptation of blacklegged ticks in the United States.e17460e1746010.1111/mec.17460Tick vectors and tick-borne disease are increasingly impacting human populations globally. An important challenge is to understand tick movement patterns, as this information can be used to improve management and predictive modelling of tick population dynamics. Evolutionary analysis of genetic divergence, gene flow and local adaptation provides insight on movement patterns at large spatiotemporal scales. We develop low coverage, whole genome resequencing data for 92 blacklegged ticks, Ixodes scapularis, representing range-wide variation across the United States. Through analysis of population genomic data, we find that tick populations are structured geographically, with gradual isolation by distance separating three population clusters in the northern United States, southeastern United States and a unique cluster represented by a sample from Tennessee. Populations in the northern United States underwent population contractions during the last glacial period and diverged from southern populations at least 50 thousand years ago. Genome scans of selection provide strong evidence of local adaptation at genes responding to host defences, blood-feeding and environmental variation. In addition, we explore the potential of low coverage genome sequencing of whole-tick samples for documenting the diversity of microbial pathogens and recover important tick-borne pathogens such as Borrelia burgdorferi. The combination of isolation by distance and local adaptation in blacklegged ticks demonstrates that gene flow, including recent expansion, is limited to geographical scales of a few hundred kilometres.© 2024 The Author(s). Molecular Ecology published by John Wiley & Sons Ltd.SchovilleSean DSD0000-0001-7364-434XDepartment of Entomology, University of Wisconsin-Madison, Madison, Wisconsin, USA.BurkeRussell LRLDepartment of Biology, Hofstra University, Hempstead, New York, USA.DongDahn-YoungDYDepartment of Integrative Biology, University of Wisconsin-Madison, Madison, Wisconsin, USA.GinsbergHoward SHSUnited States Geological Survey, Eastern Ecological Science Center, Woodward Hall - PSE, Field Station at the University of Rhode Island, Kingston, Rhode Island, USA.MaestasLaurenLCattle Fever Tick Research Laboratory, USDA, Agricultural Research Service, Edinburg, Texas, USA.PaskewitzSusan MSMDepartment of Entomology, University of Wisconsin-Madison, Madison, Wisconsin, USA.TsaoJean IJIDepartment of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan, USA.Department of Large Animal Clinical Sciences, Michigan State University, East Lansing, Michigan, USA.engEEID EF-0914476Directorate for Biological SciencesU01 CK000505CCCDC HHSUnited StatesWIS04035U.S. Department of AgricultureE20193274-00Michigan Department of Health and Human ServicesU01 CK000505CCCDC HHSUnited StatesJournal Article20240704