PREDICTING EXTINCTION TIMES FROM ENVIRONMENTAL STOCHASTICITY AND CARRYING-CAPACITY
PREDICTING EXTINCTION TIMES FROM ENVIRONMENTAL STOCHASTICITY AND CARRYING-CAPACITY
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DOI：
10.1046/j.1523-1739.1994.08010124.x
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发表时间：
1994-03-01
影响因子：
6.3
通讯作者：
FOLEY, P
中科院分区：
文献类型：
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作者：
FOLEY, P
小种群的管理者通常需要估计其种群的预期灭绝时间T（e）。灭绝时间的有用模型必须在生态学上是现实的，并依赖于可测量的参数。许多种群由于环境的随机性而灭绝，即使当承载力K是稳定的，预期增长率是正的。提出了一个模型，通过对数种群大小n（t）（= log（e）N（t））的扩散分析给出T（e）。模型种群根据方程N（t+1）= R（t）N（t）增长，以K为上限。模型的应用需要估计参数k = logK，r（d）= n的预期变化，v（r）=方差（log R），rho为r（t）的自相关。这些数据可以很容易地从年度人口普查数据中计算出来（r（d）是最难估计的）。导出了T（e）的一般公式。作为一种特殊情况，当环境波动超过预期增长（即r（d）几乎等于0）时，T（e）= 2n 0（k-n 0/2）/v（r）。如果r（t）是自相关的，则有效方差v（re）几乎等于v（r）（1 + rho）/（1 - rho）。该理论适用于种群的棋盘斑蝶，灰熊，狼和美洲狮。
Managers of small populations often need to estimate the expected time to extinction T(e) of their charges. Useful models for extinction times must be ecologically realistic and depend on measurable parameters. Many populations become extinct due to environmental stochasticity, even when the carrying capacity K is stable and the expected growth rate is positive. A model is proposed that gives T(e) by diffusion analysis of the log population size n(t) (= log(e) N(t)). The model population grows according to the equation N(t+1) = R(t)N(t), with K as a ceiling. Application of the model requires estimation of the parameters k = logK, r(d) = the expected change in n, v(r) = Variance(log R), and rho the autocorrelation of the r(t). These are readily calculable from annual census data (r(d) is trickiest to estimate). General formulas for T(e) are derived. As a special case, when environmental fluctuations overwhelm expected growth (that is r(d) almost-equal-to 0), T(e) = 2n0(k - n0/2)/v(r). If the r(t) are autocorrelated, then the effective variance is v(re) almost-equal-to v(r) (1 + rho)/(1 - rho). The theory is applied to populations of checkerspot butterfly, grizzly bear, wolf and mountain lion.