DOES ENVIRONMENTAL STOCHASTICITY MATTER - ANALYSIS OF RED DEER LIFE-HISTORIES ON RUM
DOES ENVIRONMENTAL STOCHASTICITY MATTER - ANALYSIS OF RED DEER LIFE-HISTORIES ON RUM
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DOI：
10.1007/bf01237655
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发表时间：
1995-11-01
影响因子：
1.9
通讯作者：
CLUTTONBROCK, TH
中科院分区：
文献类型：
--
作者：
BENTON, TG;GRANT, A;CLUTTONBROCK, TH
大多数生活史理论假设，生物体环境的短期变化不会影响生物体的生存和繁殖力。这种假设很少被满足。在这里，我们调查的人口和进化生物学的红鹿，马鹿elephas，看看放松这一假设可能会作出重大差异，预测进化生物学的这个物种。为了做到这一点，我们使用了21年的数据，从鹿的朗姆酒，西部群岛，苏格兰的人口。在随机环境中的人口增长率估计使用Tuljapurkar的小噪声近似，证实了自举模拟。数值微分被用来观察选择压力（即种群增长率对生命率变化的敏感性）在随机和确定性情况下是否不同。这些数据还可以用来估算复制成本。这些成本，作为权衡纳入敏感性分析，允许调查不同的生活史策略的进化效益。环境引起的随机变化的红鹿的生命率会导致轻微的减少（类似或等于1%）的预测人口增长率和估计的选择压力对鹿的生活史几乎没有影响。因此，我们的结论是，即使人口密度无关的随机效应是显着的，鹿的健身并没有显着的影响，这些和他们适应的平均条件，他们的经验。然而，所选择的生活史是敏感的权衡目前的繁殖力，生存和未来的繁殖力，它很可能是环境的变化将影响这些权衡，从而影响生活史的选择。我们还表明，目前的平均生活史是非最佳的，并建议这是一个选择的压力所施加的淘汰和捕食，现在大大减少的结果。由于在这种情况下使用随机或确定性方法提供类似的估计数，因此使用后者是合理的。因此，r（年人均人口增长率）是随机数值波动的人口适应度的适当度量。在一个种群规模不变的情况下，终生繁殖成功率是一个显而易见的衡量适合度的标准。
Most life-history theory assumes that short-term variation in an organism's environment does not affect the survivorships and fecundities of the organisms. This assumption is rarely met. Here we investigate the population and evolutionary biology of red deer, Cervus elephas, to see if relaxation of this assumption is likely to make significant differences to the predicted evolutionary biology of this species. To do this we used 21 years of data from a population of deer on Rum, Western Isles, Scotland. Population growth rates in a stochastic environment were estimated using Tuljapurkar's small noise approximation, confirmed by bootstrap simulation. Numerical differentiation was used to see if the selection pressures (i.e, sensitivities of population growth rate to changes in the vital rates) differ between the stochastic and deterministic cases. The data also allow the costs of reproduction to be estimated. These costs, incorporated as trade-offs into the sensitivity analysis, allow investigation of evolutionary benefits of different life-history tactics. Environmentally induced stochastic variation in the red deer vital rates causes a slight reduction (similar or equal to 1%) in the predicted population growth rate and has little impact on the estimated selection pressures on the deer's life-history. We thus conclude that, even though density-independent stochastic effects on the population are marked, the deer's fitness is not markedly affected by these and they are adapted to the average conditions they experience. However, the selected life-history is sensitive to the trade-offs between current fecundity, survivorship and future fecundity and it is likely that the environmental variance will affect these trade-offs and, thus, affect the life-history favoured by selection. We also show that the current average life-history is non-optimal and suggest this is a result of selection pressures exerted by culling and predation, now much reduced. As the use of stochastic or deterministic methods provide similar estimates in this case, the use of the latter is justified. Thus, r (the annual per capita rate of population growth) is an appropriate measure of fitness in a population with stochastic numerical fluctuations. In a population of constant size lifetime reproductive success is the obvious measure of fitness to use.