Influence of plant quality on pine sawfly population dynamics
Influence of plant quality on pine sawfly population dynamics
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植物品质对松叶蜂种群动态的影响
DOI：
10.1034/j.1600-0706.2000.890303.x
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发表时间：
2000
期刊：
影响因子：
3.4
通讯作者：
C. Björkman
中科院分区：
文献类型：
--
作者：
S. Larsson;B. Ekbom;C. Björkman
植物品质对草食昆虫种群动态的贡献一直是一个备受争议的问题。许多研究已经记录了不同的植物质量如何不同地影响昆虫个体的生存和繁殖力。然而，这种影响是否可以转化为昆虫种群的水平尚不清楚。为了检验这一假设，需要将个人和群体层面的过程结合起来。这对于经验方法来说是困难的，但可以通过建模来实现，因为两个级别的组织都存在适当的数据。在本文中，我们报告了一个模型，该模型用于分析樟子松 (Pinus sylvestris) 质量的改变是否有助于欧洲松叶蜂 (Neodiprion sertifer) 种群的增加。锯蝇幼虫对可变植物质量（即针状树脂酸浓度）反应的实验数据用于参数化模型。在高树脂酸浓度下，幼虫的存活率和锯蝇的繁殖力都会降低。然而，高树脂酸浓度同时也是有益的，因为幼虫对捕食者的防御能力得到增强。在该模型中，个人反应数据与人口层面的文献数据相结合；与茧捕食相关的 III 型功能反应被认为是调节锯蝇种群的密度依赖性过程。分析表明，当针树脂酸浓度（r）或幼虫捕食压力（p）较低时，爆发的风险较高。当 r 或 p 高时，没有风险。通过分析不同的情况，发现 r 和 p 的微小变化可能导致锯蝇种群从低爆发风险转向高爆发风险。实证研究中观察到 r 具有相同或更大幅度的变化。还考虑了三营养相互作用的作用。这是通过消除树脂酸对模型中幼虫性能的积极影响来实现的。研究发现，与没有这种防御的昆虫相比，N. sertifer 的反捕食者防御使其在更广泛的 r 和 p 组合下更容易爆发。我们得出的结论是，密度无关因素（例如针化学）的微小变化可能对草食动物种群动态产生重大影响，因为针质量引起的繁殖力和存活率的增加可能使种群逃脱密度依赖因素（例如茧捕食）的控制。
The contribution of plant quality to the population dynamics of herbivorous insects has been an issue of much controversy. Many studies have documented how variable plant quality differentially influences the survival and fecundity of insect individuals. Whether or not such effects can be translated to the level of insect populations is, however, not clear. In order to test this hypothesis one needs to combine processes at both the level of the individual and the population. This is difficult with an empirical approach, but could be achieved by means of modeling given that appropriate data exist for both levels of organization. In this paper we report on a model developed to analyze whether altered Scots pine (Pinus sylvestris) quality can contribute to the build-up of populations of the European pine sawfly (Neodiprion sertifer). Experimental data on responses of sawfly larvae to variable plant quality, i.e. needle concentrations of resin acids, were used to parameterize the model. Larval survival and sawfly fecundity are reduced at high resin acid concentrations. However, high resin acid concentrations are, at the same time, beneficial because larval defense against predators is enhanced. In the model, data on individual responses were combined with literature data at the population level; a type III functional response related to cocoon predation was presumed to be the density-dependent process regulating sawfly populations. The analysis showed that the risk for an outbreak is high when needle resin acid concentration (r) or larval predation pressure (p) is low. When r or p is high there is no risk. By analyzing different scenarios it was found that small changes in r and p can result in the sawfly population moving from low to high outbreak risk. Changes of the same, or larger, magnitude in r have been observed in empirical studies. The role of tritrophic interactions was also considered. This was done by removing the positive effects of resin acids on larval performance in the model. It was found that the anti-predator defense of N. sertifer makes it prone to outbreak under wider combinations of r and p than an insect without the defense. We conclude that small changes in a density-independent factor, such as needle chemistry, can have significant effects on herbivore population dynamics because increased fecundity and survival caused by needle quality may allow the population to escape the control of density-dependent factors, such as cocoon predation.