quinquefasciatus and Cx. tarsalis are most abundant in riparian habitats, but that Cx. quinquefasciatus shows higher relative abundance than Cx. tarsalis in residential habitats [44]. We also noted that Cx. quinquefasciatus was typically the most abundant mosquito species in our urban collections, consistent Vandetanib VEGFR inhibitor with the observations of Reisen et al. [44]. Another possible explanation for the large differences in genetic diversity among Sonoran Desert Culex., which is not mutually exclusive of the above hypothesis, may be related to differences in population histories. Culex tarsalis is native to North America, whereas both Cx. quinquefasciatus and Cx. pipiens probably evolved in Africa [6]. Ross [45] hypothesized that Cx. quinquefasciatus was introduced from Africa via the slave trade within the last few centuries.

This hypothesis, however, has been challenged [5]. Regardless of the dispersal route, if Cx. quinquefasciatus is a relatively recent arrival to the New World [8], it is possible that it would still retain the genetic signature of a founder event (i.e., reduced genetic variability) compared with the indigenous Cx. tarsalis.A recent study reported the presence of Cx. pipiens, and hybrids between Cx. pipiens and Cx. quinquefasciatus, in Mexico City [46]. Given the close association of both species with humans, together with their potential for dispersal via commercial air traffic, clear patterns of global distributions of the two species and their hybrids [5] may become progressively obscured. Figure 2 shows that COI barcode sequences are unable to distinguish between the two species.

Although a possibility thus exists that our samples are Cx. pipiens, or hybrids of Cx. pipiens and Cx. quinquefasciatus, a more thorough examination of individuals of the Cx. pipiens complex from this region with specific molecular markers that reliably separate the two cryptic species [5, 8, 10] will be required before this can be resolved.Females of several species of Culex from North America, including Cx. restuans Theobald, Cx. nigripalpus Theobald, and Cx. salinarius Coquillett, are often indistinguishable from those of the Cx. pipiens complex and can easily be confused [5, 10]. Barcode sequences, however, have been shown to be useful for separating and identifying species of Culicidae, with interspecific K2P divergences of COI generally showing values ��2% [11, 12, 47].

Based on the 2% cutoff, we provisionally assigned the unidentified lineages to Culex sp. 1 and sp. 2 (mean d = 2.1%), but further molecular and morphological studies will be required to confirm their identity. We have shown, however, that Culex sp. 1 Batimastat and sp. 2, which were initially identified as Cx. quinquefasciatus based on morphological examination, are very closely related to Cx. nigripalpus from the Dominican Republic (Figure 2) and only more distantly related to the other Culex species shown in Figure 2.