The genus Culex contains 768 described species, many of which (198) are grouped in the subgenus Culex, and important gaps still exist in our knowledge of their taxonomy and relationships selleckchem U0126 [3, 4]. In the Cx. pipiens complex, the species-level taxa present in the New World are Cx. pipiens and Cx. quinquefasciatus which show an extensive zone of hybridization at mid latitudes in the USA [5�C7]. Some authors, however, place Cx. quinquefasciatus as a subspecies of Cx. pipiens [8]. Here they are treated as separate species. Culex quinquefasciatus is widely distributed, found in southern USA, Mexico, Central America, and most of South America [5]. Culex quinquefasciatus and Cx. tarsalis have markedly different histories in the Sonoran Desert, as well as elsewhere in the New World, and a comparison of their population genetics is predicted to reveal patterns reflecting these differences.

Culex tarsalis is native to North America, whereas both Cx. pipiens and Cx. quinquefasciatus are thought to have evolved in Africa [6]. Although the route and timing of the postulated arrival of the Cx. pipiens complex to the New World are controversial [8], if Cx. quinquefasciatus is a relatively recent arrival to the New World it may still retain the genetic signature of a founder event. Our primary goal in the present study was to utilize mitochondrial DNA (mtDNA) sequences from a segment of the cytochrome c oxidase subunit I (COI) gene, known as the barcode segment [9], to examine population genetics of Culex mosquitoes collected from widely separated localities in the Sonoran Desert region, including the Baja California peninsula, mainland Sonora, Mexico and southeastern Arizona, USA, to test the prediction that Cx.

quinquefasciatus and Cx. tarsalis will show evidence of different demographic histories. Because we found extremely low genetic variability in the COI gene in Cx. quinquefasciatus, we also used a small set of nuclear microsatellite loci to obtain preliminary Carfilzomib estimates of population structure in this species. Also, because it is well known that taxonomic identifications based on morphological examination of females of certain species of Culex can be especially problematic [5, 10], COI barcodes, which can reliably distinguish many nominal species of Culex [11, 12], were used to estimate the overall biodiversity and phylogenetic relationships of Culex obtained in our survey.2. Materials and Methods2.1. SamplingAdult female mosquitoes were collected at seven localities, including the states of Sonora (Hermosillo, Guaymas, Ciudad Obreg��n, and Navojoa) and Baja California Sur (Bah��a Tortugas and Santa Rosal��a) in Mexico and southeastern Arizona (Tucson) in the USA (Figure 1).