Eutrophication and predator presence overrule the effects of temperature on mosquito survival and development

Adequate predictions of mosquito-borne disease risk require an understanding of the relevant drivers governing mosquito populations. Since previous studies have focused mainly on the role of temperature, here we assessed the effects of other important ecological variables (predation, nutrient availability, presence of conspecifics) in conjunction with the role of temperature on mosquito life history parameters. We carried out two mesocosm experiments with the common brown house mosquito, Culex pipiens, a confirmed vector for West Nile Virus, Usutu and Sindbis, and a controphic species; the harlequin fly, Chironomus riparius. The first experiment quantified interactions between predation by Notonecta glauca L. (Hemiptera: Notonectidae) and temperature on adult emergence. The second experiment quantified interactions between nutrient additions and temperature on larval mortality and adult emergence. Results indicate that 1) irrespective of temperature, predator presence decreased mosquito larval survival and adult emergence by 20–50%, 2) nutrient additions led to a 3-4-fold increase in mosquito adult emergence and a 2-day decrease in development time across all temperature treatments, 3) neither predation, nutrient additions nor temperature had strong effects on the emergence and development rate of controphic Ch. riparius. Our study suggests that, in addition to of effects of temperature, ecological bottom-up (eutrophication) and top-down (predation) drivers can have strong effects on mosquito life history parameters. Current approaches to predicting mosquito-borne disease risk rely on large-scale proxies of mosquito population dynamics, such as temperature, vegetation characteristics and precipitation. Local scale management actions, however, will require understanding of the relevant top-down and bottom-up drivers of mosquito populations.精准预测蚊媒疾病风险，需明晰调控蚊虫种群的关键驱动因子。既往研究多聚焦于温度的作用，本研究则评估了捕食作用、养分可获得性、同种个体存在等重要生态变量，与温度共同对蚊虫生活史参数的影响。本研究以常见的棕尾家蚊尖音库蚊（Culex pipiens）——西尼罗河病毒、乌苏图病毒及辛德毕斯病毒的确定传播媒介——以及同营养级物种花翅摇蚊（Chironomus riparius）为研究对象，开展了两项中宇宙实验。第一项实验量化了大仰泳蝽（Notonecta glauca L.，半翅目：仰泳蝽科）的捕食作用与温度对蚊虫成虫羽化的交互影响；第二项实验则量化了养分添加与温度对蚊虫幼虫死亡率及成虫羽化的交互影响。研究结果显示：1）无论温度条件如何，捕食者的存在均可使蚊虫幼虫存活率与成虫羽化率降低20%~50%；2）在所有温度处理组中，养分添加可使蚊虫成虫羽化量提升3~4倍，并将发育时长缩短2天；3）捕食作用、养分添加及温度均未对同营养级花翅摇蚊的羽化情况与发育速率产生显著影响。本研究表明，除温度效应外，生态系统的自下而上（富营养化，即养分富集）与自上而下（捕食作用）驱动因子，均可对蚊虫生活史参数产生显著调控作用。当前蚊媒疾病风险预测模型多依赖温度、植被特征与降水量等蚊虫种群动态的大尺度替代指标，但局部尺度的防控措施，则需明晰调控蚊虫种群的自上而下与自下而上驱动因子。