Species delimitation in a species complex of Culicoides biting midges

There are many different theories on what constitutes a species; however, this distinction can have far- reaching effects on policymaking, conservation efforts, and surveillance. A multifaceted approach to species delimitation can often add clarity to issue such as cryptic species or species complexes. Culicoides biting midges are small flies capable of transmitting pathogens in many livestock systems. In North America, the main vector species is C. sonorensis whichbelongs to a complex of species that have both morphological and molecular similarities. Single nucleotide polymorphism (SNP) data from individual Culicoides collected across the US and Canada identified two additional cryptic species within the existing three species of this complex. The inability to differentiate these cryptic species from the vector species has undoubtedly affected vector competency estimates, species distribution maps, and vector surveillance efforts. Interestingly, there was discordance between the SNP and mitochondrial data which explains why barcoding these species has had limited success. Based on these molecular identifications, we highlight subtle morphological and overt ecological differences that support these findings. The larval habitats within this species complex are vastly different and could be evidence of speciation through ecological niche partitioning. Finally, species-specific microsatellite markers were developed to rapidly, and economically, differentiate the non-vector species from C. sonorensis. Continued study of the speciation of closely related vector and non-vector species will produce valuable evolutionary insights into vector competency as well as improve current surveillance programs.