A rural–urban latitudinal study of the distributions of Culex quinquefasciatus and Culex pipiens bioforms in their southernmost sympatric fringe

Abstract

Mosquitoes grouped in the complex Culex pipiens L. (Diptera: Culicidae) are important vectors of medical and veterinary diseases. In the South American sympatric region, Cx. pipiens and Culex quinquefasciatus Say coexist and potentially hybridize. To identify key drivers of their geographical distribution, mosquito immatures were collected from flower vases of eight urban/rural cemetery pairs within a 5° latitudinal transect along Buenos Aires Province, Argentina. The specimens were identified by molecular methods and their relative proportion modelled as a function of environmental variables. At the beginning of the warm season, northern and southern cemeteries presented exclusively Cx. quinquefasciatus and Cx. pipiens, respectively, with different proportions of both at mid latitudes. By the end of the summer, Cx. quinquefasciatus was present throughout the study area, exclusively in 11 of the 16 cemeteries both rural and urban, whereas Cx. pipiens was predominant only in the southernmost pair. Mean annual temperature, photoperiod variability and time of the season were key drivers of their distributions. All specimens of Cx. pipiens were identified as form molestus and no hybrids were recognized. The reported distribution patterns and the potential absence of Cx. pipiens f. pipiens and hybrids are discussed, along with their implications in disease transmission.

Blood feeding patterns of the Culex pipiens complex in equestrian land uses and their implications for arboviral encephalitis risk in temperate Argentina

“…quinquefasciatus present mainly in the northern extreme and Cx. pipiens molestus predominant in the south (Cardo et al, 2016; Cardo, Rubio, Junges, et al, 2020). Previous works have also described a differential distribution of the members of the complex as a function of the urbanization gradient, with Cx.…”

“…pipiens bioforms, Cx. quinquefasciatus and their hybrids were differentiated by PCR targeting the acetylcholinesterase-2 gene (protocol I, Smith & Fonseca, 2004) and the flanking region of the CQ11 microsatellite (protocol II, Bahnck & Fonseca, 2006) as previously described (Cardo, Rubio, Junges, et al, 2020). The first protocol amplifies a 610 bp band for Cx.…”

“…So far, only the bioform molestus of Cx. pipiens has been identified (Cardo, Rubio, Junges, et al, 2020; Cardo, Rubio, Vezzani, & Carbajo, 2020; Micieli et al, 2013). In areas where both members converge, fertile hybrids are reported (Almirón et al, 1995; Cardo et al, 2018; Micieli et al, 2013).…”

Assessment of Culex pipiens bioforms in the world’s southernmost distribution limit

“…Previous studies in Buenos Aires Province identified specimens from La Plata City (34.87ºS, 57.90ºW) as form molestus by a full microsatellite analysis, (17) whereas the individuals collected in 13 cemeteries throughout the province were also identified as molestus using the CQ11 locus. (18) Although no previous attempts to identify Cx. pipiens bioforms had been made in Patagonia, Mitchell et al (19) reported a high degree of autogeny and proof of anthropophily in a colony established from mosquitoes collected at 43ºS.…”

Host–mosquito interactions in rural and urban equestrian facilities from temperate Argentina

“…All abdomens were processed for bloodmeal identification as specified below, and only the heads and thoraces from the members of the Cx. pipiens complex were further processed by molecular techniques to identify the complex member as has been previously described (Cardo et al, 2020). Although the taxonomical status of the complex members is debatable (Harbach, 2012), herein each will be referred to as a ‘species’ in a general sense.…”