Urban population structure and dispersal of an Australian mosquito (Aedes notoscriptus) involved in disease transmission

Dispersal is critical for successful pest control measures as it
determines the rate of movement across target control areas and influences
the risk of human exposure. We used a fine-scale spatial population
genomic approach to investigate the dispersal ecology and population
structure of Aedes notoscriptus, an important
disease-transmitting mosquito at the Mornington Peninsula, Australia. We
sampled and reared Ae. notoscriptus eggs at two time
points from 170 traps up to 5 km apart and generated genomic data from 240
individuals. We also produced a draft genome assembly from a laboratory
colony established from mosquitoes sampled near the study area. We found
low genetic structure (Fst) and high coancestry throughout the study
region. Using genetic data to identify close kin dyads, we found that
mosquitoes had moved distances of >1 km within a generation, which
is further than previously described. A spatial autocorrelation analysis
of genetic distances indicated genetic similarity at >1 km
separation, a tenfold higher distance than for a comparable population of
Ae. aegypti, from Cairns, Australia. These findings point to high
mobility of Ae. notoscriptus, highlighting challenges of
localized intervention strategies. Further sampling within the same area 6
and 12 months after initial sampling showed that egg-counts were
relatively consistent across time, and that spatial variation in
egg-counts covaried with spatial variation in Wright’s neighbourhood size
(NS). As NS increases linearly with population density, egg-counts may be
useful for estimating relative density
in Ae. notoscriptus. The results highlight the
importance of acquiring species-specific data when planning control
measures.

扩散行为对于有害生物防控措施的成功实施至关重要，其决定了有害生物在目标防控区域内的移动速率，同时也会影响人类的暴露风险。本研究采用精细尺度空间种群基因组学方法，探究了澳大利亚莫宁顿半岛地区一种重要的传病蚊类——诺氏伊蚊（Aedes notoscriptus）的扩散生态学与种群结构。研究团队在相距最远达5公里的170个诱捕器中，于两个时间点采集并孵化了诺氏伊蚊（Ae. notoscriptus）的卵粒，随后对240个个体开展了基因组测序并获取相关基因组数据。此外，本研究从采自研究区域附近的蚊株建立的实验室种群中，构建了该物种的基因组草图组装序列。研究结果显示，整个研究区域内的遗传分化程度较低（Fst），且共祖率较高。通过基因组数据鉴定近缘亲缘配对个体，我们发现该蚊种在一个世代内的移动距离超过1公里，这一结果较此前已有报道的结果更远。对遗传距离的空间自相关分析表明，遗传相似性可在相距超过1公里的个体间被检测到，这一距离较澳大利亚凯恩斯地区埃及伊蚊（Aedes aegypti）的同类种群高出10倍。上述研究结果表明诺氏伊蚊（Ae. notoscriptus）具有较强的移动能力，这凸显了局部干预策略所面临的挑战。在初始采样后的6个月与12个月对同一区域开展的后续采样显示，卵粒计数结果在不同时间点相对稳定，且卵粒计数的空间变异与赖特邻域大小（Wright’s neighbourhood size, NS）的空间变异呈协同变化。由于赖特邻域大小与种群密度呈线性正相关，因此卵粒计数可用于估算诺氏伊蚊（Ae. notoscriptus）的相对种群密度。本研究结果强调了在制定防控措施前获取物种特异性数据的重要性。