D3024: (1st Place) Turning up the heat: A comparison of larval thermal tolerance between Culex pipiens and Culex quinquefasciatus

Culex pipiens and quinquefasciatus are abundant and closely related vectors of West Nile virus, with notable differences in vector competence between the two species and their hybrids.Cx. quinquefasciatus and hybrids exhibit higher transmission rates than Cx. pipiens. In North America, Cx. pipiens are predominantly found north of 36 degrees latitude, while Cx. quinquefasciatus reside mostly south of 39 degrees, creating a broad hybrid zone between these latitudes. As temperature is a likely driver of these distributions, the anticipated effects of climate change could trigger changes in range boundaries and the hybrid zone. Understanding these future range shifts is vital for public health due to variable vector competence.

The mosquito's larval stage is particularly vulnerable to temperature fluctuations due to limited dispersal ability. Despite this, comparative studies on thermal tolerance in Cx. pipiens and quinquefasciatus larvae are lacking. We measured the median lethal temperature (LT50) in larvae from five Culex pipiens assemblage populations along a latitudinal gradient using a temperature ramping protocol.

Our findings suggest that upper thermal tolerance limits are dependent on the collection site, with southern Cx. quinquefasciatus populations showing significantly greater resistance to rising temperatures than northern Cx. pipiens populations. We found a strong correlation between median lethal temperature, latitude, and summer temperatures at collection sites, suggesting local climate adaptation. Our results can contribute to predictive models regarding shifts in Culex pipiens assemblage distributions under future warming scenarios.