The effects of disturbance and enemy exclusion on performance of an invasive species, common ragweed, in its native range
The effects of disturbance and enemy exclusion on performance of an invasive species, common ragweed, in its native range
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DOI：
10.1007/s00442-009-1557-9
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发表时间：
2010-04-01
期刊：
影响因子：
2.7
通讯作者：
Kotanen, Peter M.
中科院分区：
文献类型：
--
作者：
MacDonald, A. Andrew M.;Kotanen, Peter M.
普通豚草（Ambrosia artemisiifolia）在其本土北美是一种丰富的杂草，尽管它支持广泛的天敌。在这里，我们测试了这些敌人是否对这种植物在其原生范围内的表现有重大影响。在一系列的田间实验中，我们将这种一年生植物的三个主要生活史阶段（种子、幼苗和成虫）中的天敌排除在外；在成虫期，我们还对土壤扰动和同密度进行了控制。然后，我们测量了这些治疗对生长、生存和繁殖的影响。与对照区相比，将真菌和脊椎动物的种子排除在土壤表面并不会提高种子的萌发率。排除软体动物和其他食草动物后，幼苗存活率仅略有增加。杀虫剂减少了对成虫叶片的伤害，但没有改善其生长和繁殖。干扰显著提高了成虫的生长和成虫存活率，而同种密度的增加则降低了成虫的生长和成虫存活率。这些结果表明豚草对许多天敌的攻击不敏感，这有助于解释它在本土的成功。此外，他们认为，尽管豚草在入侵欧洲时失去了大部分的食叶昆虫，但逃离这些敌人不太可能提供显著的人口优势；相反，骚乱可能是其入侵的一个更重要的因素。不应假定从敌人身上逃脱是外来物种成功的原因，除非也能证明它们的表现有所改善；母语学习可以帮助实现这一目标。
Common ragweed (Ambrosia artemisiifolia) is an abundant weed in its native North America, despite supporting a wide range of natural enemies. Here, we tested whether these enemies have significant impacts on the performance of this plant in its native range. We excluded enemies from the three principal life-history stages (seed, seedling, and adult) of this annual in a series of field experiments; at the adult stage, we also manipulated soil disturbance and conspecific density. We then measured the consequences of these treatments for growth, survival, and reproduction. Excluding fungi and vertebrate granivores from seeds on the soil surface did not increase germination relative to control plots. Seedling survivorship was only slightly increased by the exclusion of molluscs and other herbivores. Insecticide reduced damage to leaves of adult plants, but did not improve growth or reproduction. Growth and survivorship of adults were strongly increased by disturbance, while higher conspecific density reduced performance in disturbed plots. These results indicate ragweed is insensitive to attack by many of its natural enemies, helping to explain its native-range success. In addition, they suggest that even though ragweed lost most of its insect folivores while invading Europe, escape from these enemies is unlikely to have provided a significant demographic advantage; instead, disturbance is likely to have been a much more important factor in its invasion. Escape from enemies should not be assumed to explain the success of exotic species unless improved performance also can be demonstrated; native-range studies can help achieve this goal.