Species delimitation and mitonuclear discordance within a species complex of biting midges

Abstract

The inability to distinguish between species can be a serious problem in groups responsible for pathogen transmission. Culicoides biting midges transmit many pathogenic agents infecting wildlife and livestock. In North America, the C. variipennis species complex contains three currently recognized species, only one of which is a known vector, but limited species-specific characters have hindered vector surveillance. Here, genomic data were used to investigate population structure and genetic differentiation within this species complex. Single nucleotide polymorphism data were generated for 206 individuals originating from 17 locations throughout the United States and Canada. Clustering analyses suggest the occurrence of two additional cryptic species within this complex. All five species were significantly differentiated in both sympatry and allopatry. Evidence of hybridization was detected in three different species pairings indicating incomplete reproductive isolation. Additionally, COI sequences were used to identify the hybrid parentage of these individuals, which illuminated discordance between the divergence of the mitochondrial and nuclear datasets.

Using Zoos as Sentinels for Re-Emerging Arboviruses: Vector Surveillance during an Outbreak of Epizootic Hemorrhagic Disease at the Minnesota Zoo

“…One important caveat for this study is the recent elevation of Culicoides albertensis to the species level. This species had previously been synonymized with C. sonorensis but was re-elevated to the species status after the collection of compelling genetic data [ 39 ]. Due to the close morphological similarity between C. albertensis and other members of the C. variipennis complex, it is possible that this species was present within the study area but was unable to be morphologically distinguished.…”

Immigration and seasonal bottlenecks: High inbreeding despite high genetic diversity in an oscillating population of the biting midge,Culicoides sonorensis(Diptera: Ceratopogonidae)

“…Most biting midge species studied thus far, including C. sonorensis, are associated with an absence of genetic differentiation between geographically distant populations (Jacquet et al 2015, Onyango et al 2015a, Jacquet et al 2016, Shults et al 2021b, which reduces the possibility that the elevated inbreeding coefficient resulted from the Wahlund effect (i.e., sub-structuring within a population). Alternatively, the high level of inbreeding has often been attributed to the presence of a high number of microsatellite null alleles (i.e., an allele that consistently fails to amplify using PCR), as these can cause significant heterozygote deficits relative to HWE (Onyango et al 2015a, Mignotte et al 2021.…”

“…This region of California has been very active in dairy production for many years (Gerry and Mullens 2000), and as such, there is a possibility that this population favors genes beneficial to utilizing artificial habitats. The overall genetic differentiation between C. sonorensis populations across the entire US is relatively low (Shults et al 2021b), and an adaptation to livestock breeding habitats could help explain the range-wide genetic homogeneity and elevated inbreeding. Though inbreeding is generally associated with low genetic diversity, this is not what was observed in this population.…”

“…Most biting midge species studied so far exhibit long-distance dispersal, often wind-mediated (Ducheyne et al 2007, Sanders and Carpenter 2014, Jacquet et al 2016), leading to high gene flow among populations and an absence of population differentiation even at continental scales (Jacquet et al 2015, Onyango et al 2015a, Shults et al 2021b). Despite the absence of genetic differentiation among most populations, high levels of inbreeding coefficient ( F IS ) and heterozygote deficiencies are commonly found in Culicoides species (Onyango et al 2015b, Mignotte et al 2021, Shults et al 2021b). This is similarly reported for some mosquito species (Lehmann et al 1997, Porretta et al 2007, Fonseca et al 2009, Goubert et al 2016).…”

Species boundaries to the limit: validating species delimitation methods is critical to avoid taxonomic inflation in the genomic era

“…Based on those results, T. hajarensis was suggested to be a species complex with at least three allopatric lineages: one in the Western and Central Hajars, a second in the Central and Eastern Hajars, and another one in the easternmost side of the Hajar Mountains and in Masirah Island (de Pous et al, 2016). However, mitochondrial evolutionary history is not always linked to its nuclear counterpart, with common cases of mito-nuclear discordances across phyla (Marshall, Chambers, Matz, & Hillis, 2021; Shults et al, 2022). This stresses the need of revisiting this group’s systematics with NGS techniques, which recover large portions or the complete nuclear genome and are key to determine whether there are mito-nuclear discordances, providing a comprehensive perspective of the evolutionary history of a species.…”