High-resolution environmental and host-related factors impacting questing Ixodes scapularis at their northern range edge

The geographic range of tick populations has expanded in Canada due to climate warming and the associated poleward range shifts of their vertebrate hosts. Abiotic factors, such as temperature, precipitation, and snow, are known to directly affect tick abundance. Yet, biotic factors, such as the abundance and diversity of mammal hosts, may also alter tick abundance and consequent tick-borne disease risk. Here, we incorporated host surveillance data with high-resolution environmental data to evaluate the combined impact of abiotic and biotic factors on questing Ixodes scapularis abundance in Ontario and Quebec, Canada. High-resolution abiotic factors were derived from remote sensing satellites and meteorological towers, while biotic factors related to mammal hosts were derived from active surveillance data that we collected in the field. Generalized additive models were used to determine the relative importance of abiotic and biotic factors on questing I. scapularis abundance. Combinations of abiotic and biotic factors were identified as important drivers of abundances of questing I. scapularis. Positive and negative linear relationships were found for questing I. scapularis abundance with precipitation and accumulated snow, but no effect was found for the relative abundance of white-footed mice. Positive relationships were also identified between questing I. scapularis abundance with monthly mean precipitation and mammal species richness. Therefore, future studies that assess I. scapularis should incorporate host surveillance data with high-resolution environmental factors to determine the key drivers impacting the abundance and geographic spread of tick populations and tick-borne pathogens.

Methods
Broad-scale remote sensing data were extracted from MODIS to determine the values of land surface temperature, total evapotranspiration, and enhanced vegetation indices. This data was extracted and processed in ArcMap and then further processed in R.

Data was extracted from meteorological towers through Environment and Climate Change Canada, which was processed in R.

Data from field surveys were processed in R.

受气候变暖及其伴随的脊椎动物宿主极地范围迁移影响，加拿大蜱虫种群的地理分布范围已出现扩张。已知非生物因子（abiotic factors），如温度、降水与积雪，可直接影响蜱虫种群数量。然而，生物因子（biotic factors），如哺乳动物宿主的丰度与多样性，同样可能改变蜱虫种群数量，进而影响蜱传疾病的传播风险。本研究整合宿主监测数据与高分辨率环境数据，旨在评估非生物与生物因子对加拿大安大略省和魁北克省寻宿主肩突硬蜱（Ixodes scapularis）种群数量的联合影响。其中，高分辨率非生物因子来源于遥感卫星与气象塔观测数据，而与哺乳动物宿主相关的生物因子则来源于本研究团队野外采集的主动监测数据。本研究采用广义加性模型，以明确非生物与生物因子对寻宿主肩突硬蜱种群数量的相对重要性。研究发现，非生物与生物因子的组合是调控寻宿主肩突硬蜱种群数量的关键驱动因素。寻宿主肩突硬蜱种群数量与降水、积雪累积量分别呈现正负线性相关关系，但未发现白足鼠相对丰度对其存在显著影响。此外，寻宿主肩突硬蜱种群数量与月均降水量及哺乳动物物种丰富度呈正相关关系。因此，未来开展肩突硬蜱（I. scapularis）相关研究时，应整合宿主监测数据与高分辨率环境因子，以明确影响蜱虫种群数量、地理扩散及蜱传病原体传播的核心驱动因素。

方法
本研究从中分辨率成像光谱仪（MODIS）提取大范围遥感数据，以获取地表温度、总蒸散量及增强型植被指数的相关数值。该数据通过ArcMap进行提取与预处理，随后在R语言中完成进一步处理。
研究数据还来源于加拿大环境与气候变化部（Environment and Climate Change Canada）的气象塔观测数据，该类数据同样在R语言中完成处理。
野外调查所获数据亦在R语言中进行预处理。