When there is no escape: The effects of natural enemies on native, invasive, and noninvasive plants
When there is no escape: The effects of natural enemies on native, invasive, and noninvasive plants
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DOI：
10.1890/06-1377
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发表时间：
2007-05-01
期刊：
影响因子：
4.8
通讯作者：
Gilbert, Gregory S.
中科院分区：
文献类型：
--
作者：
Parker, Ingrid M.;Gilbert, Gregory S.
生物入侵研究中的一个重要问题是，成功的入侵在多大程度上可以用天敌的控制下的释放来解释。天敌主导了两种交替现象的解释：大多数引入的植物未能建立可行的种群（生物抗性假说），一些引入的植物成为有害的入侵者（天敌假说）。我们使用了一套18个遗传相关的本地和规范的三叶草（三叶草和苜蓿）和叶面病原体和无脊椎食草动物攻击他们回答两个问题。在同一地点，本地物种是否比引进物种遭受更大的天敌攻击？一些引进的物种是否因为容易受到当地天敌的影响而被排除在本地植物群落之外？我们使用三条证据线来解决这些问题：（1）在四年的普通花园实验中，每个三叶草物种的真菌病原体和食草动物的攻击频率和组成，以及对接种普通病原体的敏感性;（2）在普通花园实验中每个物种遭受的叶片损伤程度;（3）利用相关方法和病原菌去除实验估计适合度效应。引进物种没有表现出从病原体逃逸的证据，作为一个组在感染水平，易感性，疾病流行，疾病的严重程度（与更严重的损害引进物种在一年），疾病对死亡率的影响，和杀真菌剂处理对死亡率和生物量的影响方面相当于本地物种。相比之下，无脊椎动物草食动物造成更多的本地物种在两年的损害，虽然草食动物的攻击对死亡率的影响没有本地和引进物种之间的差异。在引进的物种，生物抗性假说的预测不支持：最具侵略性的物种表现出更大的感染，更大的患病率和疾病的严重程度，更普遍的草食动物，更大的影响，杀真菌剂对生物量和无创引进的物种在所有其他方面没有区别。因此，虽然草食动物更喜欢本地引进的物种，逃避害虫的压力不能用来解释为什么一些引进的三叶草是常见的入侵者在沿海草原，而其他人不是。
An important question in the study of biological invasions is the degree to which successful invasion can be explained by release from control by natural enemies. Natural enemies dominate explanations of two alternate phenomena: that most introduced plants fail to establish viable populations (biotic resistance hypothesis) and that some introduced plants become noxious invaders (natural enemies hypothesis). We used a suite of 18 phylogenetically related native and normative clovers (Trifolium and Medicago) and the foliar pathogens and invertebrate herbivores that attack them to answer two questions. Do native species suffer greater attack by natural enemies relative to introduced species at the same site? Are some introduced species excluded from native plant communities because they are susceptible to local natural enemies? We address these questions using three lines of evidence: (1) the frequency of attack and composition of fungal pathogens and herbivores for each clover species in four years of common garden experiments, as well as susceptibility to inoculation with a common pathogen; (2) the degree of leaf damage suffered by each species in common garden experiments; and (3) fitness effects estimated using correlative approaches and pathogen removal experiments. Introduced species showed no evidence of escape from pathogens, being equivalent to native species as a group in terms of infection levels, susceptibility, disease prevalence, disease severity (with more severe damage on introduced species in one year), the influence of disease on mortality, and the effect of fungicide treatment on mortality and biomass. In contrast, invertebrate herbivores caused more damage on native species in two years, although the influence of herbivore attack on mortality did not differ between native and introduced species. Within introduced species, the predictions of the biotic resistance hypothesis were not supported: the most invasive species showed greater infection, greater prevalence and severity of disease, greater prevalence of herbivory, and greater effects of fungicide on biomass and were indistinguishable from noninvasive introduced species in all other respects. Therefore, although herbivores preferred native over introduced species, escape from pest pressure cannot be used to explain why some introduced clovers are common invaders in coastal prairie while others are not.