Consequences of herbivory by native ungulates for the reproduction of a savanna tree
Consequences of herbivory by native ungulates for the reproduction of a savanna tree
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DOI：
10.1111/j.1365-2745.2006.01196.x
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发表时间：
2007-01-01
影响因子：
5.5
通讯作者：
Palmer, Todd M.
中科院分区：
文献类型：
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作者：
Goheen, Jacob R.;Young, Truman P.;Palmer, Todd M.
1食草动物可能会通过减少个体植物的生存、生长和繁殖对植物种群产生负面影响。2在非洲稀树草原，大型哺乳动物食草动物的进食一再显示会减少这些系统中的优势树木金合欢属成员的成年生存和生长。然而，哺乳动物食草动物对金合欢繁殖的潜在成本在很大程度上是未被探索的，并且从未在非洲稀树草原进行过实验研究。3使用长期，大规模的实地实验，我们证明，在没有本地食草动物的情况下，个体树木繁殖的可能性是两倍，并且繁殖的树木产生了更大的种子生物量。此外，棘长度（过去的草食动物的指标）与减少繁殖的金合欢drepanolobium，占主导地位的树木在东非大面积。本地食草动物的浏览触发了更长的刺的产生，这是一种诱导抗性，刺的长度与繁殖的发生和数量显著负相关。4诱导抗性似乎减轻了大型食草动物存在的食草动物的负面影响：在没有浏览器的情况下，具有长刺的树木的繁殖水平与具有类似长刺长度的树木相当。抑制成年金合欢的生长，因此通常被认为是维持非洲稀树草原树木和草的共同优势的关键。我们的研究结果提供了第一个实验证据，大型哺乳动物食草动物可以抑制繁殖金合欢，从而突出了一个额外的途径，通过这些食草动物可能会影响人口动态的这个重要和广泛的gen.6在稀树草原系统，大型食草动物的人口下降可能会引发一系列复杂的人口统计学反应的树木，具有潜在的强大后果的结构和功能的稀树草原。
1 Herbivores may negatively impact plant populations by reducing the survival, growth and reproduction of individual plants.2 In African savannas, browsing by large mammalian herbivores has been shown repeatedly to reduce adult survival and growth of members of the genus Acacia, the dominant trees in these systems. However, the potential costs of mammalian herbivory to Acacia reproduction are largely unexplored, and have never been investigated experimentally in African savannas.3 Using a long-term, large-scale field experiment, we demonstrate that, in the absence of native herbivores, individual trees were twice as likely to reproduce, and those that reproduced produced a greater biomass of seeds. In addition, spine length (an indicator of past herbivory) was correlated with reduced reproduction of Acacia drepanolobium, the dominant tree across large areas of East Africa. Browsing by native herbivores triggers the production of longer spines, an induced resistance, and spine length was significantly and negatively related both to the occurrence and magnitude of reproduction.4 Induced resistance appeared to mitigate the negative effects of herbivory where large herbivores were present: trees with long spines reproduced at levels comparable to trees with similarly long spine lengths in the absence of browsers.5 Large mammalian herbivores kill and suppress the growth of adult Acacia, and therefore often are regarded as critical in maintaining the co-dominance of trees and grasses in African savannas. Our results provide the first experimental evidence that large mammalian herbivores can suppress reproduction in Acacia, thus highlighting an additional pathway through which these herbivores might impact population dynamics of this important and widespread genus.6 In savanna systems, declining populations of large herbivores may trigger a series of complex demographic responses for trees, with potentially strong consequences for the structure and function of savannas.