ARTHROPOD DYNAMICS ON SAGEBRUSH (ARTEMISIA-TRIDENTATA) - EFFECTS OF PLANT CHEMISTRY AND AVIAN PREDATION
ARTHROPOD DYNAMICS ON SAGEBRUSH (ARTEMISIA-TRIDENTATA) - EFFECTS OF PLANT CHEMISTRY AND AVIAN PREDATION
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DOI：
10.2307/2937110
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发表时间：
1991-09-01
影响因子：
6.1
通讯作者：
REDAK, RA
中科院分区：
文献类型：
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作者：
WIENS, JA;CATES, RG;REDAK, RA
我们进行了一项田间实验，以评估在俄勒冈州中部的艾草(Artemisia Tridentata)上出现的节肢动物的丰度和多样性与叶组织次生化学、鸟类捕食之间的相互关系。节肢动物被从个别灌木中移除，其中一些然后被关进笼子里，以排除鸟类。第二次化学和节肢动物采样间隔长达56wk后，默认/笼养处理。回收率不同的节肢动物分类群和功能群。一些吸液的同翅目和半翅目昆虫在处理后2-4周内达到对照水平，而寄生蜂和捕食者的数量仅在处理后6周恢复到与对照数量相匹配。几种草食性咀嚼叶类群(主要是鳞翅目幼虫)的丰度在处理后56wk仍显著降低。在实验结束时，食腐动物(甲螨)在缺水灌木上比在对照灌木上达到更多的数量。在净化处理后，几种化合物的浓度或出现频率也发生了显着变化。大多数灌木中存在的几种碳氢化合物、倍半萜和单萜在处理后4wk内在叶组织中的浓度急剧下降，而一些在对照植物中出现频率相对较低的醇和酮(芳樟醇、冰片、侧柏酮)在节肢动物去除后出现频率显著增加。这两个变化在实验期间都持续了下来。我们发现节肢动物类群或类群的丰度或出现与次生化合物的浓度或频率之间存在几个显著的关联，但这些关联在咀嚼叶子的鳞翅目昆虫中最为普遍。我们认为，灌木对食草性、咀嚼叶的节肢动物的移除是通过改变化学分配模式来做出反应的；化学变化持续了一年多，因为这些草食动物对退化的植物的再定殖率很慢。笼养处理的效果要不明显得多。在这个系统中，已知构成鸟类猎物的节肢动物多样性在受保护的灌木上的恢复速度慢于暴露的灌木，但在退耕一年后，受保护的灌木的多样性已增加到更高的水平。在笼养和未笼养灌木中，几乎没有节肢动物类群或功能群在丰度或出现频率上存在差异，尽管在实验结束时，受保护灌木上的食真菌(不被鸟类吃掉)数量增加到几乎是未笼养对照的两倍。灌丛间鸟类捕食性类群的丰富度和多样性在裸露灌丛中的差异大于受保护灌丛，这可能反映了鸟类对区域限制搜索的影响。笼养灌木与未笼养灌木的叶组织次生化学成分差异不显著。
We conducted a field experiment to assess interrelationships between leaf-tissue secondary chemistry, avian predation, and the abundance and diversity of arthropods occurring on sagebrush (Artemisia tridentata) in central Oregon. Arthropods were removed from individual shrubs, some of which were then caged to exclude birds. Secondary chemistry and arthropods were sampled at intervals up to 56 wk following the defaunation/caging treatment.Recovery rates differed among arthropod taxa and functional groups. Several sap-sucking homopterans and hemipterans reached control levels within 2-4 wk of the treatment, whereas abundances of parasitoids and predators recovered to match control numbers only 6 wk after defaunation. Abundances of several herbivorous leaf-chewing taxa (primarily lepidopteran larvae) remained significantly depressed even 56 wk after the treatment. Fungivores (oribatid mites) reached greater abundances on defaunated than on control shrubs by the end of the experiment. There were also significant changes in the concentrations or frequency of occurrence of several chemical compounds following the defaunation treatment. Several hydrocarbons, sesquiterpenes, and monoterpenes that were present in most shrubs exhibited sharply reduced concentrations in leaf tissues within 4 wk of the treatment, whereas some alcohols and ketones (linalool, borneol, thujone), which occurred at relatively low frequencies among control plants, increased dramatically in their frequencies of occurrence following arthropod removal. Both changes persisted for the duration of the experiment. We found several significant associations between the abundance or occurrence of arthropod taxa or groups and concentrations or frequencies of secondary compounds, but these were most prevalent among the leaf-chewing lepidopterans. We suggest that the shrubs responded to the removal of herbivorous, leaf-chewing arthropods by altering chemical allocation patterns; the changes in chemistry persisted for over a year because recolonization of the defaunated plants by these herbivores was slow.Effects of the caging treatment were much less obvious. The recovery of the diversity of arthropods known to constitute prey for birds in this system was slower on shrubs protected from avian predation than on exposed shrubs, but a year after defaunation diversity had increased to higher levels on the protected shrubs. Few arthropod taxa or functional groups differed in abundance or frequency of occurrence between caged and uncaged shrubs, although fungivores (which are not eaten by birds) increased to levels on protected shrubs that were nearly twice those on the uncaged controls by the end of the experiment. Between-shrub variance in the abundance and diversity of bird-prey taxa was greater among exposed than protected shrubs, possibly reflecting the effects of area-restricted searching by the birds. There were no differences in leaf-tissue secondary chemistry between caged and uncaged shrubs.