Department of Biology, University of Vermont, Burlington, VT 05405, USA.
Conserv Biol. 2012 Feb;26(1):47-56. doi: 10.1111/j.1523-1739.2011.01715.x. Epub 2011 Jul 28.
Assessing species survival status is an essential component of conservation programs. We devised a new statistical method for estimating the probability of species persistence from the temporal sequence of collection dates of museum specimens. To complement this approach, we developed quantitative stopping rules for terminating the search for missing or allegedly extinct species. These stopping rules are based on survey data for counts of co-occurring species that are encountered in the search for a target species. We illustrate both these methods with a case study of the Ivory-billed Woodpecker (Campephilus principalis), long assumed to have become extinct in the United States in the 1950s, but reportedly rediscovered in 2004. We analyzed the temporal pattern of the collection dates of 239 geo-referenced museum specimens collected throughout the southeastern United States from 1853 to 1932 and estimated the probability of persistence in 2011 as <6.4 × 10(-5) , with a probable extinction date no later than 1980. From an analysis of avian census data (counts of individuals) at 4 sites where searches for the woodpecker were conducted since 2004, we estimated that at most 1-3 undetected species may remain in 3 sites (one each in Louisiana, Mississippi, Florida). At a fourth site on the Congaree River (South Carolina), no singletons (species represented by one observation) remained after 15,500 counts of individual birds, indicating that the number of species already recorded (56) is unlikely to increase with additional survey effort. Collectively, these results suggest there is virtually no chance the Ivory-billed Woodpecker is currently extant within its historical range in the southeastern United States. The results also suggest conservation resources devoted to its rediscovery and recovery could be better allocated to other species. The methods we describe for estimating species extinction dates and the probability of persistence are generally applicable to other species for which sufficient museum collections and field census results are available.
评估物种的生存状况是保护计划的一个重要组成部分。我们设计了一种新的统计方法，用于从博物馆标本的时间序列中估计物种持续存在的概率。为了补充这种方法，我们为确定是否存在缺失或据称已经灭绝的物种开发了定量停止规则。这些停止规则基于对目标物种进行搜索时遇到的共存物种数量的调查数据。我们用象牙喙啄木鸟（Campephilus principalis）的案例研究来说明这两种方法，长期以来，人们认为这种鸟在美国 20 世纪 50 年代已经灭绝，但据报道在 2004 年又重新被发现。我们分析了 1853 年至 1932 年期间在美国东南部采集的 239 个地理参考博物馆标本的采集日期的时间模式，并估计 2011 年的持续存在概率<6.4×10(-5)，可能灭绝日期不晚于 1980 年。从自 2004 年以来对啄木鸟进行搜索的 4 个地点的鸟类普查数据（个体数量的计数）分析中，我们估计在 3 个地点（路易斯安那州、密西西比州、佛罗里达州各 1 个）可能仍有 1-3 个未被发现的物种。在康加里河（南卡罗来纳州）的第四个地点，在对 15500 只鸟类个体进行计数后，没有出现单一物种（只有一个观测值的物种），这表明已经记录的物种数量（56 个）不太可能随着额外的调查工作而增加。总的来说，这些结果表明，在东南地区，象牙喙啄木鸟目前存在于其历史范围内的可能性几乎为零。结果还表明，将资源用于重新发现和恢复象牙喙啄木鸟可能会更好地分配给其他物种。我们描述的用于估计物种灭绝日期和持续存在概率的方法通常适用于其他具有足够博物馆收藏和实地普查结果的物种。
