Phylogeography and Climate-Driven Distribution of Culex tarsalis (Diptera: Culicidae): Implications for the Global Spread of West Nile Virus.

objectiveTo evaluate mitochondrial genetic diversity, exploratory phylogeographic structure, and the current and future climatic suitability of Culex tarsalis. MATERIALS AND

methodsWe analyzed 406 COI sequences (475 bp) to estimate haplotype diversity (Hd), nucleotide diversity (π), and neutrality (Tajima's D). Given the use of a single mitochondrial locus, population structure analyses (STRUCTURE and DAPC) were treated as exploratory assessments of haplotype frequency patterns rather than inferential population genetic models. Ecological niche models (MaxEnt) were used to estimate current and future climatic suitability under multiple climate scenarios.

resultsA total of 120 haplotypes were identified, with higher diversity observed in the United States. However, strong geographic sampling imbalance limits direct comparisons among countries. Negative Tajima's D values were consistent with demographic expansion or purifying selection. Exploratory clustering suggested geographic structuring of mitochondrial haplotypes, although this pattern should be interpreted cautiously due to marker and sampling limitations. Ecological niche models indicated high suitability across North America and predicted broader potential suitability across temperate and arid regions globally. Future projections suggested a latitudinal shift and moderate expansion of suitable areas under high-emission scenarios.

conclusionC. tarsalis exhibits geographically structured mitochondrial variation and broad climatic suitability, but inference of population structure and dispersal processes is constrained by the use of a single marker and uneven sampling. These results highlight the importance of integrating genomic data and surveillance frameworks to assess future invasion risks.