title: Evidence for a population expansion in the West Nile virus vector Culex tarsalis.
abstract: Population genetic structure of the West Nile Virus vector Culex tarsalis was investigated in 5 states in the western United States using 5 microsatellite loci and a fragment of the mitochondrial reduced form of nicotinamide adenine dinucleotide dehydrogenase 4 (ND4) gene. ND4 sequence analysis revealed a lack of isolation by distance, panmixia across all populations, an excess of rare haplotypes, and a star-like phylogeny. Microsatellites revealed moderate genetic differentiation and isolation by distance, with the largest genetic distance occurring between populations in southern California and New Mexico (F(ST) = 0.146). Clustering analysis and analysis of molecular variance on microsatellite data indicated the presence of 3 broad population clusters. Mismatch distributions and site-frequency spectra derived from mitochondrial ND4 sequences displayed pattern's characteristic of population expansion. Fu and Li's D* and F*, Fu's F(S), and Tajima's D statistics performed on ND4 sequences all revealed significant, negative deviations from mutation-drift equilibrium. Microsatellite-based multilocus heterozygosity tests showed evidence of range expansion in the majority of populations. Our results suggest that C. tarsalis underwent a range expansion across the western United States within the last 375,000-560,000 years, which may have been associated with Pleistocene glaciation events that occurred in the midwestern and western United States between 350,000 and 1 MYA.
authors.affiliation: The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, USA.
authors.forename: Meera
authors.initials: M
authors.lastname: Venkatesan
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Westbrook
authors.forename: M Claire
authors.initials: MC
authors.lastname: Hauer
authors.forename: Jason L
authors.initials: JL
authors.lastname: Rasgon
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003465:Culex / Q000201:enzymology / Q000235:genetics / Q000821:virology; D004272:DNA, Mitochondrial; D051456:Gene Flow; D014644:Genetic Variation; D006239:Haplotypes; D007303:Insect Vectors / Q000235:genetics / Q000821:virology; D015810:Linkage Disequilibrium; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D009245:NADH Dehydrogenase / Q000235:genetics; D010802:Phylogeny; D011110:Polymorphism, Genetic; D011157:Population Dynamics; D014481:United States; D014901:West Nile Fever / Q000635:transmission / Q000821:virology; D014902:West Nile virus
chemical_list: D004272:DNA, Mitochondrial; C098483:NADH dehydrogenase subunit 4; D009245:NADH Dehydrogenase