Population-specific vital rate contributions influence management of an endangered ungulate
Population-specific vital rate contributions influence management of an endangered ungulate
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DOI：
10.1890/09-1107.1
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发表时间：
2010-09-01
影响因子：
5
通讯作者：
Wehausen, John D.
中科院分区：
文献类型：
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作者：
Johnson, Heather E.;Mills, L. Scott;Wehausen, John D.
为了制定有效的管理战略，以恢复受威胁和濒危物种，关键是要确定哪些生命率(生存和繁殖参数)对种群表现不佳负有责任，以及哪些种群的增长将最有效地改变种群的发展轨迹。然而，在实际应用中，确定关键生命率的方法往往受到人口数据不足、人口动力学渐近和平均生命率变化相等、微小变化等不切实际的假设的限制。我们在一项对联邦濒危的内华达山脉大角羊(Ovis Candensis Sierrae)的动态最重要的生命率的分析中，评估了这些限制的后果。基于1980年至2007年收集的数据，我们估计了三个孤立群体的生命率，考虑了抽样误差、方差和协方差。我们使用了分析敏感性分析、生命阶段模拟分析和一种新的非渐近模拟方法来(1)确定亚种恢复的目标生命率；(2)评估濒危大角羊相对于其他有蹄类种群的生命率模式；(3)评估渐近和非渐近模型在满足短期管理目标方面的性能；以及(4)模拟提高大角羊种群增长率的管理场景。我们发现大角羊的生命率在空间和时间上有很大的差异，导致它们对不同种群的重要性不同。结果，内华达山脉大角羊表现出不符合理论预期或在其他有蹄类动物中观察到的种群特定动态。我们的研究表明，来自大的、增长的或健康的种群的生命频率推断可能不适用于那些小的、下降的或濒危的种群。我们还发现，虽然渐近方法一般适用于大角羊保护规划，但我们的非渐近种群模型产生了对管理者来说非常重要的意外结果。最后，个体大角羊种群动态的极端差异意味着，濒危物种恢复的有效管理战略可能往往需要针对特定种群。
To develop effective management strategies for the recovery of threatened and endangered species, it is critical to identify those vital rates (survival and reproductive parameters) responsible for poor population performance and those whose increase will most efficiently change a population's trajectory. In actual application, however, approaches identifying key vital rates are often limited by inadequate demographic data, by unrealistic assumptions of asymptotic population dynamics, and of equal, infinitesimal changes in mean vital rates. We evaluated the consequences of these limitations in an analysis of vital rates most important in the dynamics of federally endangered Sierra Nevada bighorn sheep (Ovis canadensis sierrae). Based on data collected from 1980 to 2007, we estimated vital rates in three isolated populations, accounting for sampling error, variance, and covariance. We used analytical sensitivity analysis, life-stage simulation analysis, and a novel non-asymptotic simulation approach to (1) identify vital rates that should be targeted for subspecies recovery; (2) assess vital rate patterns of endangered bighorn sheep relative to other ungulate populations; (3) evaluate the performance of asymptotic vs. non-asymptotic models for meeting short-term management objectives; and (4) simulate management scenarios for boosting bighorn sheep population growth rates. We found wide spatial and temporal variation in bighorn sheep vital rates, causing rates to vary in their importance to different populations. As a result, Sierra Nevada bighorn sheep exhibited population-specific dynamics that did not follow theoretical expectations or those observed in other ungulates. Our study suggests that vital rate inferences from large, increasing, or healthy populations may not be applicable to those that are small, declining, or endangered. We also found that, while asymptotic approaches were generally applicable to bighorn sheep conservation planning, our non-asymptotic population models yielded unexpected results of importance to managers. Finally, extreme differences in the dynamics of individual bighorn sheep populations imply that effective management strategies for endangered species recovery may often need to be population-specific.