Ecological characterization and molecular differentiation of Culex pipiens complex taxa and Culex torrentium in eastern Austria

Abstract

BackgroundCulex pipiens complex taxa differ in behaviour, ecophysiology and epidemiologic importance. Despite their epidemiologic significance, information on genetic diversity, occurrence and seasonal and spatial distribution patterns of the Cx. pipiens complex is still insufficient. Assessment of seasonal and spatial distribution patterns of Culex pipiens forms and their congener Cx. torrentium is crucial for the understanding of their vector–pathogen dynamics.MethodsFemale mosquitoes were trapped from April–October 2014 twice a month for a 24-h time period with BG-sentinel traps at 24 sampling sites in eastern Austria, using carbon dioxide as attractant. Ecological forms of Cx. pipiens s.l. and their hybrids were differentiated using the CQ11 locus, and Cx. pipiens forms and their congener Cx. torrentium using the ACE-2 gene. Differential exploitation of ecological niches by Cx. pipiens forms and Cx. torrentium was analysed using likelihood ratio tests. Possible effects of environmental parameters on these taxa were tested using PERMANOVA based on distance matrices and, if significant, were modelled in nMDS ordination space to estimate non-linear relationships.ResultsFor this study, 1476 Culex spp. were sampled. Culex pipiens f. pipiens representing 87.33 % of the total catch was most abundant, followed by hybrids of both forms (5.62 %), Cx. torrentium (3.79 %) and Cx. pipiens f. molestus (3.25 %). Differences in proportional abundances were found between land cover classes. Ecological parameters affecting seasonal and spatial distribution of these taxa in eastern Austria are precipitation duration, air temperature, sunlight and the interaction term of precipitation amount and the Danube water level, which can be interpreted as a proxy for breeding habitat availability.ConclusionsThe Cx. pipiens complex of eastern Austria comprises both ecologically different forms, the mainly ornithophilic form pipiens and the mainly mammalophilic and anthropophilic form molestus. Heterogeneous agricultural areas as areas of coexistence may serve as hybridization zones, resulting in potential bridge vectors between birds and humans. Occurrence, seasonal and spatial distribution patterns of the Cx. pipiens complex and Cx. torrentium and the presence of hybrids between both forms were quantified for the first time in Austria. These findings will improve the knowledge of their vector–pathogen dynamics in this country.

The role of Culex pipiens mosquitoes in transmission of West Nile virus in Europe

“…pipiens biotypes and hybrids in aboveground habitats throughout Europe. These results are in line with previous findings from The Netherlands , Germany (Rudolf et al 2013), Austria (Zittra et al 2016), Portugal (Gomes et al 2009, Osório et al 2014), Italy (Di Luca et al 2016, and Greece (Gomes et al 2013a). There was a clear gradient of decreasing biotype pipiens and increasing biotype molestus proportions from northern to southern latitudes.…”

“…Studies that place traps at random locations throughout a country are more useful to get insight in local variation and dynamics of Cx. pipiens within a country (Di Luca et al 2016, Osório et al 2014, Rudolf et al 2013, Zittra et al 2016.…”

“…Several studies have now focused on biotype composition in different countries in Europe (Di Luca et al 2016, Gomes et al 2013a, Gomes et al 2009, Osório et al 2014, Rudolf et al 2013, Vogels et al 2016b, Zittra et al 2016. Thus far, most of these studies (including chapters 2 and 3) presented the average population composition, by combining data from mosquito collections of varying periods of time.…”

“…Thus far, in-depth studies that differentiated between the biotypes were done at country level (Di Luca et al 2016, Gomes et al 2013a, Osório et al 2014, Rudolf et al 2013, Zittra et al 2016. Few of these studies systematically compared biotype ratios among different habitat types (Di Luca et al 2016, Osório et al 2014, Zittra et al 2016). However, due to differences in experimental design it is hard to make direct comparisons between Cx.…”

Latitudinal Diversity of Culex pipiens Biotypes and Hybrids in Farm, Peri-Urban, and Wetland Habitats in Europe

“…Thus far, in-depth studies that differentiated between the biotypes were done at country level [19–22,26,27]. Few of these studies systematically compared biotype ratios among different habitat types [19,20,27]. However, due to differences in experimental design it is hard to make direct comparisons between Cx .…”