Centre for Biodiversity Dynamics (CBD), Norwegian University of Science and Technology (NTNU), 7491, Trondheim, Norway.
Norwegian Institute for Nature Research (NINA), 7485, Trondheim, Norway.
Acta Biotheor. 2020 Jun;68(2):227-252. doi: 10.1007/s10441-019-09366-8. Epub 2019 Sep 28.
The ecological impact of alien species is a function of the area colonised. Impact assessments of alien species are thus incomplete unless they take the spatial component of invasion processes into account. This paper describes a measure, termed expansion speed, that quantifies the speed with which a species increases its spatial presence in an assessment area. It is based on the area of occupancy (AOO) and can be estimated from grid occupancies. Expansion speed is defined as the yearly increase in the radius of a coherent circle having the same area as the AOO, irrespective of whether the increase is due to natural dispersal or anthropogenic transport. Two methods for estimating expansion speed are presented: one that requires several years of spatio-temporal observation data and explicitly takes detection rates into account; and one that can be used under a situation with sparse data. Using simulations and real-world data from natural history collections, it is shown that the method provides a good fit to observational datasets. Expansion speed has several valuable properties. Being based on AOO, it is an intuitive measure; as it only requires occupancy data, it is comparatively easy to estimate; and because it is a quantitative and generic measure, it increases the testability and comparability of impact assessments of alien species.
外来物种的生态影响是其殖民区域的函数。因此，外来物种的影响评估如果不考虑入侵过程的空间因素，将是不完整的。本文描述了一种度量标准，称为扩张速度，用于量化物种在评估区域内增加其空间存在的速度。它基于占有面积（AOO），并可通过网格占有率进行估算。扩张速度定义为具有与 AOO 相同面积的连贯圆的半径每年增加的量，无论增加是由于自然扩散还是人为运输造成的。本文提出了两种估算扩张速度的方法：一种需要多年的时空观测数据，并明确考虑检测率；另一种方法可在数据稀疏的情况下使用。使用模拟和自然历史收藏的真实数据表明，该方法与观测数据集拟合良好。扩张速度具有多个有价值的特性。它基于 AOO，是一种直观的度量标准；由于它只需要占用数据，因此相对容易估算；并且由于它是一种定量和通用的度量标准，因此增加了对外来物种影响评估的可测试性和可比性。
