Modeling Range Expansion of Hemlock Woolly Adelgid in Eastern North America 1951-2009

Range expansion by native and non-native species will continue to be a major component of global change. Anticipating the potential effects of changes in species distributions requires models capable of forecasting population spread across realistic, heterogeneous landscapes and subject to spatiotemporal variability in habitat suitability. Several decades of theory and model development, as well as increased computing power and availability of fine-resolution GIS data, now make such models possible. This R code allows simulation of the spread of the hemlock woolly adelgid (HWA, Adelges tsugae) under climatic conditions experienced from December of 1951 until March of 2009. The code describes a spatially explicit stochastic model that combines dynamic dispersal and population processes with fine-resolution maps characterizing spatiotemporal heterogeneity in winter temperature and hemlock abundance to model range expansion of HWA. The model is parameterized using multi-year datasets describing population and dispersal dynamics of HWA and is applied to eastern North America.

本土与外来物种的分布扩张仍将是全球变化的核心组成部分。要预判物种分布变化所带来的潜在影响，需构建可在真实异质性景观中预测种群扩散，且可纳入生境适宜性时空变异的模型。历经数十年的理论与模型研发，加之计算能力的提升与高分辨率地理信息系统（GIS，Geographic Information System）数据的可及性增强，如今这类模型已具备实现条件。本R代码可模拟1951年12月至2009年3月期间，铁杉球蚜（hemlock woolly adelgid, HWA, Adelges tsugae）的扩散过程。该代码所描述的是一款空间显式随机模型，结合动态扩散与种群动态过程，并辅以表征冬季温度与铁杉丰度时空异质性的高分辨率地图，以此模拟铁杉球蚜的分布扩张。该模型基于描述铁杉球蚜种群与扩散动态的多年数据集进行参数化，并应用于北美东部区域。