Locking life-cycles onto seasons: Circle-map models of population dynamics and local adaptation
Locking life-cycles onto seasons: Circle-map models of population dynamics and local adaptation
复制标题
将生命周期锁定在季节上：人口动态和当地适应的圆图模型
DOI：
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
R. Nisbet
中科院分区：
文献类型：
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作者：
W. Gurney;P. Crowley;R. Nisbet
我们已经制定了一个模型，描述了在简要semelparous生物的发展速度主要是由环境因素控制的成熟和繁殖的时间。该模型被表示为一个圆形的地图在连续几代的成熟时间。这张地图的性质使我们能够确定暴露于有规律的季节性环境中的种群成员的生命周期之间预期的同步程度，我们已经证明，具有由一系列连续阶段组成的生命史的生物体，所有阶段的发育都由相同的季节性功能驱动，不能将它们的生命周期与季节相锁定。然而，如果生物体表现出由Norling提出的临界时间/临界发育机制引起的兼性滞育，（1984 a，B，c），则它总是成功地锁相到一个完全周期的驱动函数.在这个圆图模型的背景下，我们研究了试图在一个不适当的生活史阶段越冬所引起的种群灭绝，或者试图在一年中不可能繁殖的时候繁殖。我们已经证明，这种预防的可能性限制了后临界阶段的短暂性和临界时间的延迟性，我们已经研究了作为临界时间和发展的函数的持久性队列的适应性。我们发现，如果后临界阶段比前临界阶段更危险，那么自然选择倾向于一个短的后临界阶段和一个晚的临界时间;这个过程的限制取决于成功繁殖的生长季节的比例，我们已经确定了与最佳生活史参数相对应的成熟模式随生命周期长度（因此纬度或海拔）的变化。我们发现，对于只能在生长季节的一小部分成熟的生物体，任何纬度梯度的大多数都表现出单峰成熟模式。在生长季节的大部分时间里能够成熟和繁殖的生物表现出更复杂的模式，但仍然表现出单峰或双峰模式最佳的纬度范围。
We have formulated a model describing the timing of maturity and reproduction in briefly semelparous organisms whose development rate is primarily controlled by environmental factors. The model is expressed as a circle-map relating time of year at maturation in successive generations. The properties of this map enable us to determine the degree of synchrony to be expected between the life-cycles of members of a population exposed to a regular seasonal environment.We have proved that organisms with a life-history composed of a contiguous series of stages, all with development driven by the same seasonal function, cannot phase-lock their life-cycles to the seasons. However if the organism exhibits facultative diapause induced by a critical time/critical development mechanism of the type proposed by Norling (1984a,b,c) then it will always succeed in phase-locking to a perfectly periodic driving function.Within the context of this circle-map model we have examined population extinctions caused by attempting to over-winter in an inappropriate life-history stage, or by attempting to reproduce at a time of year when this is impossible. We have shown that the possibility of such extinctions limits both the shortness of the post-critical stage, and the lateness of the critical time.We have examined the fitness of persistent cohorts as a function of critical time and development. We find that if the post-critical stage is riskier than the pre-critical then natural selection favors a short post-critical stage and a late critical time; the limitation of this process being dependent on the proportion of the growing season over which successful reproduction is possible.We have determined the variation with life-cycle length (and hence latitude or altitude) of the maturation pattern corresponding to optimal life-history parameters. We find that for organisms which can mature only over a small part of the growing season the majority of any latitudinal gradient exhibits a unimodal maturation pattern. Organisms which can mature and reproduce over the majority of the growing season exhibit more complex patterns, but still exhibit substantial ranges of latitude over which unimodal or bimodal patterns are optimal.