Environmental and Life Sciences, Trent University, 1600 West Bank Drive, Peterborough, Ontario K9J 7B8, Canada.
Mol Ecol Resour. 2012 Jul;12(4):686-96. doi: 10.1111/j.1755-0998.2012.03123.x. Epub 2012 Feb 22.
A cost or resistance surface is a representation of a landscape's permeability to animal movement or gene flow and is a tool for measuring functional connectivity in landscape ecology and genetics studies. Parameterizing cost surfaces by assigning weights to different landscape elements has been challenging however, because true costs are rarely known; thus, expert opinion is often used to derive relative weights. Assigning weights would be made easier if the sensitivity of different landscape resistance estimates to relative costs was known. We carried out a sensitivity analysis of three methods to parameterize a cost surface and two models of landscape permeability: least cost path and effective resistance. We found two qualitatively different responses to varying cost weights: linear and asymptotic changes. The most sensitive models (i.e. those leading to linear change) were accumulated least cost and effective resistance estimates on a surface coded as resistance (i.e. where high-quality elements were held constant at a low-value, and low-quality elements were varied at higher values). All other cost surface scenarios led to asymptotic change. Developing a cost surface that produces a linear response of landscape resistance estimates to cost weight variation will improve the accuracy of functional connectivity estimates, especially when cost weights are selected through statistical model fitting procedures. On the other hand, for studies where cost weights are unknown and model selection is not being used, methods where resistance estimates vary asymptotically with cost weights may be more appropriate, because of their relative insensitivity to parameterization.
成本或阻力表面是对动物运动或基因流动的景观渗透性的表示，是衡量景观生态学和遗传学研究中功能连通性的工具。通过为不同的景观元素分配权重来参数化成本表面一直具有挑战性，因为真实成本很少被知晓；因此，通常使用专家意见来推导出相对权重。如果知道不同景观阻力估计值对相对成本的敏感性，那么分配权重将变得更加容易。我们对三种参数化成本表面的方法和两种景观渗透性模型（最小成本路径和有效阻力）进行了敏感性分析。我们发现了两种不同的对变化的成本权重的响应：线性和渐近变化。最敏感的模型（即导致线性变化的模型）是在编码为阻力的表面上累积的最小成本和有效阻力估计值（即高质量元素保持在低值，低质量元素在较高值处变化）。所有其他成本表面方案都导致渐近变化。开发一种成本表面，使其对成本权重变化的景观阻力估计值产生线性响应，将提高功能连通性估计的准确性，特别是在通过统计模型拟合程序选择成本权重时。另一方面，对于成本权重未知且不使用模型选择的研究，阻力估计值随成本权重渐近变化的方法可能更为合适，因为它们对参数化的相对不敏感。
