Bias in species range estimates from minimum convex polygons: implications for conservation and options for improved planning
Bias in species range estimates from minimum convex polygons: implications for conservation and options for improved planning
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DOI：
10.1017/s1367943003003044
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发表时间：
2003-02-01
影响因子：
3.4
通讯作者：
Fox, JC
中科院分区：
文献类型：
--
作者：
Burgman, MA;Fox, JC
最小凸多边形(凸壳)是一种国际公认的估计物种范围的标准方法，特别是在仅有存在数据是唯一可用的空间显式数据的情况下。它们的主要优势之一是简单。它们用于公布面积和评估被占领栖息地的趋势，是评估物种保护状况的重要组成部分。我们通过模拟表明这些估计是有偏差的。偏差随着样本量的增加而增加，并受到物种栖息地的基本形状、位置误差的大小以及采样努力的时空分布的影响。这些误差既影响地区报表，也影响对趋势的估计。其中一些误差可以通过应用阿尔法壳来减少，阿尔法壳是凸壳的推广，但不能完全消除。阿尔法壳为排除物种范围内的不连续提供了一种明确的方法。研究了包括核估计器在内的各种备选方法的优缺点。在用于量化栖息地范围和检测范围变化时，以及当受到采样努力和空间精度的时空分布差异的影响时，凸壳显示出比a壳更大的偏差。在估计物种范围的范围和趋势时，应首选A型壳。
Minimum convex polygons (convex hulls) are an internationally accepted, standard method for estimating species' ranges, particularly in circumstances in which presence-only data are the only kind of spatially explicit data available. One of their main strengths is their simplicity. They are used to make area statements and to assess trends in occupied habitat, and are an important part of the assessment of the conservation status of species. We show by simulation that these estimates are biased. The bias increases with sample size, and is affected by the underlying shape of the species habitat, the magnitude of errors in locations, and the spatial and temporal distribution of sampling effort. The errors affect both area statements and estimates of trends. Some of these errors may be reduced through the application of alpha-hulls, which are generalizations of convex hulls, but they cannot be eliminated entirely. alpha-hulls provide an explicit means for excluding discontinuities within a species range. Strengths and weaknesses of alternatives including kernel estimators were examined. Convex hulls exhibit larger bias than a-hulls when used to quantify habitat extent and to detect changes in range, and when subject to differences in the spatial and temporal distribution of sampling effort and spatial accuracy. a-hulls should be preferred for estimating the extent of and trends in species' ranges.