Distance sampling and the challenge of monitoring butterfly populations
Distance sampling and the challenge of monitoring butterfly populations
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DOI：
10.1111/j.2041-210x.2011.00109.x
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发表时间：
2011-12-01
影响因子：
6.6
通讯作者：
Thomas, Chris D.
中科院分区：
文献类型：
--
作者：
Isaac, Nick J. B.;Cruickshanks, Katie L.;Thomas, Chris D.
1.英国蝴蝶监测计划(UKBMS)产生的丰度指数对我们了解环境变化和突出英国的保护优先事项产生了影响。在这里，我们批判性地评估UKBMS所采用的标准Pollard Walk方法。我们采用距离抽样的方法考虑了不同蝴蝶种类和生境之间的系统抽样偏差。我们在英格兰和威尔士的13个研究地点通过距离抽样收集了17个物种的5000多个观测数据。我们对检测函数进行了拟合，以探索物种和地点之间可检测性的差异。我们的结果表明，在Pollard Walk盒子里大约三分之一的个体蝴蝶被遗漏了。然而，不同物种和地点的可探测性差异很大。我们为将Pollard Walk数据转换为种群密度提供了第一个特定物种的可检测性估计。少数物种的可检测性没有下降，大多数物种只需要适度的校正系数，但对于最不能检测到的物种，我们估计有3/4的个体没有被记录下来。不同地点之间的差异很大程度上是因为英格兰地点的可探测性比威尔士的高得多，后者有不同的记录器。生物学特性在区分可检测和不可检测物种方面的解释能力有限。与真实丰度的变化相比，可探测性的变化很小，因此从Pollard Walk估计的种群密度与从距离采样得出的人口密度高度相关。这些结果被用来评估Pollard Walk的稳健性，以比较不同物种、不同地点和不同时间的丰度。UKBMS数据很好地反映了大多数物种的相对丰度和丰度的大范围趋势。我们还考虑了将距离采样应用于蝴蝶监测的可行性。距离抽样是量化偏差和不精确度的宝贵工具，并在调查受保护物种方面发挥作用，但作为志愿者记录器大规模监测多物种蝴蝶群落的更简单方法的大规模替代方法，并不可行。
1. Abundance indices generated by the UK Butterfly Monitoring Scheme (UKBMS) have been influential in informing our understanding of environmental change and highlighting UK conservation priorities. Here, we critically evaluate the standard Pollard Walk methodology employed by the UKBMS.2. We consider the systematic sampling biases among different butterfly species and biotopes using distance sampling. We collected over 5000 observations on 17 species using distance sampling at 13 study sites in England and Wales. We fitted detection functions to explore variation in detectability among species and sites.3. Our results suggest that around one-third of individual butterflies in the Pollard Walk box were missed. However, detectability varies markedly among species and sites. We provide the first species-specific estimates of detectability for converting Pollard Walk data into population densities. A few species show no drop off in detectability and most require only a modest correction factor, but for the least detectable species, we estimate that 3/4 of individuals are not recorded.4. Much of the variation among sites is explained by substantially higher detectability among sites in England than inWales, which had different recorders. Biological traits have only limited explanatory power in distinguishing detectable vs undetectable species.5. The variation in detectability is small compared with the variation in true abundance, such that population density estimates from the Pollard Walk are highly correlated with those derived from distance sampling.6. These results are used to evaluate the robustness of the Pollard Walk for comparisons of abundance across species, across sites and over time. UKBMS data provide a good reflection of relative abundance for most species and of large-scale trends in abundance. We also consider the practicalities of applying distance sampling to butterfly monitoring in general. Distance sampling is a valuable tool for quantifying bias and imprecision and has a role in surveying species of conservation concern, but is not viable as a wholesale replacement for simpler methods for large-scale monitoring of multispecies butterfly communities by volunteer recorders.