REGULATION AND STABILITY OF A FREE-LIVING HOST-PARASITE SYSTEM - TRICHOSTRONGYLUS-TENUIS IN RED GROUSE .2. POPULATION-MODELS
REGULATION AND STABILITY OF A FREE-LIVING HOST-PARASITE SYSTEM - TRICHOSTRONGYLUS-TENUIS IN RED GROUSE .2. POPULATION-MODELS
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DOI：
10.2307/5339
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发表时间：
1992-01-01
影响因子：
4.8
通讯作者：
HUDSON, PJ
中科院分区：
文献类型：
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作者：
DOBSON, AP;HUDSON, PJ
1.红鸡，Lagopus lagopus scoticus和寄生线虫，细毛圆线虫的人口动态进行了探讨，以确定是否寄生虫和主机之间的相互作用足以产生周期的松鸡丰度。两种替代模型被用来明确考虑动态的自由生活，或逮捕幼虫阶段的寄生虫。假设自由生活的幼虫的预期寿命超过2-4周，寄生虫可以很容易地在松鸡种群中建立。幼虫的寄生倾向于降低寄生虫的内在生长率，从而增加寄生虫建立所需的宿主种群的大小。当寄生虫表现出低程度的聚集和寄生虫引起的宿主繁殖力的减少大于寄生虫引起的宿主死亡率的增加时，松鸡的数量往往会循环。在模型中产生的种群周期具有在Gunnerside研究的松鸡种群的缓慢增长然后快速下降的特征。周期的周期是由松鸡种群的内在增长率和幼虫的预期寿命（模型I）。或幼虫孵化期（模型II）。循环周期随着宿主种群增长率的增加而减少，并随着自由生活的幼虫预期寿命或幼虫繁殖期的增加而延长。如果幼虫孵化时间足够长（>6个月），循环就会消亡，松鸡-线虫系统的动态非常稳定.所有的模型参数的估计可以从松鸡种群的长期记录。该模型的行为的数值分析表明，有限的逮捕幼虫阶段的模型更紧密地对应于在英格兰北部的松鸡种群。这些种群所表现出的4-5年周期将更加零星，或者在寄生虫无法建立的庄园中不存在。分析表明，在T. tenuis是一致的，它是在英格兰北部的松鸡种群中观察到的周期的原因。
1. The population dynamics of red grouse, Lagopus lagopus scoticus and the parasitic nematode, Trichostrongylus tenuis were explored to determine whether interactions between the parasite and host were sufficient to generate cycles in grouse abundance. Two alternative models were used that explicitly consider the dynamics of either the free-living, or arrested larval stages of the parasite.2. Providing that the life expectancy of the free-living larvae is more than 2-4 weeks, the parasite can readily establish in grouse populations. Larval arrestment tends to reduce the intrinsic growth rate of the parasite and thus increases the size of the host population required for the parasite to establish.3. Grouse numbers will tend to cycle when the parasites exhibit low degrees of aggregation and parasite-induced reductions in host fecundity are greater than parasite-induced increases in host mortality. The population cycles produced in the model have the slow increase followed by a rapid decline characteristic of the grouse population studied at Gunnerside.4. The period of the cycles is determined by the intrinsic growth rate of the grouse population and either larval life expectancy (Model I). or the duration of larval arrestment (Model II). Cycle periods decrease as host population growth rate increases, and lengthen with increases in either free-living larval life expectancy, or the duration of larval arrestment. If the duration of larval arrestment is sufficiently long (>6 months), the cycles die out and the dynamics of the grouse-nematode system are very stable.5. Estimates of all of the model's parameters may be made from long-term records of grouse populations. Numerical analysis of the model's behaviour suggest that a model with limited arrested larval stages more closely corresponds to the grouse populations in the North of England. The 4-5 year cycles exhibited by these populations will be more sporadic, or absent on estates where the parasite is unable to establish.6. The analysis shows that the empirical data collected on T. tenuis are consistent with it being the cause of the cycles observed in grouse populations in the North of England.