Letourneau D K
Division of Biological Control, University of California/Berkeley, 1050 San Pablo Avenue, 94706, Albany, CA, USA.
Oecologia. 1983 Oct;60(1):122-126. doi: 10.1007/BF00379331.
Myrmecophytic Piper spp. were re-examined in view of what has become a common expectation in studies of mutualistic ant-plant associations: overtly aggressive behavioral traits in ants that function in anti-herbivore defense. Piper plants provide food and shelter for the Pheidole ant inhabitants. The ants, small and "sluggish", were previously thought to serve in nutrient procurement for the plant even though their foraging is probably restricted to the plant surface and most of the ants' food is produced by the plant itself.An alternative hypothesis, that Pheidole ants function in anti-herbivore defense by disrupting herbivores as eggs or early instars occurring on Piper foliage, was tested using the following lines of reasoning: (1) If the youngest, tender leaves are more vulnerable to herbivore attack, or simply more valuable to the plant, then ants may "patrol" these leaves preferentially. More ants were found on young leaves ([Formula: see text]=2.00 ants/leaf) than on mature leaves ([Formula: see text]=0.51). (2) If the ants are functioning in anti-herbivore defense, herbivory should be lower on occupied plants than on plants without ants. Estimates of mean percent foliovore damage per sapling showed that for samples with similar average heights (and presumably, ages), the unoccupied plants had significantly greater damage. A comparison of newest leaves showed a significant trend for damage to decrease with increased ant activity. (3) If ants are attacking hervibores at early stages of development, baiting with eggs should demonstrate this activity. Over 75% of all egg baits on young and mature leaves were taken up by an ant during observation periods of 30 or 60 min. Baits were found significantly faster on young than on mature leaves. In over half of the baiting trials, the egg was taken to the edge of the leaf and dropped to the ground rather than sequestered as a nutrient source.These data suggest that Pheidole inhabiting Piper plants are important in plant defense from herbivores and that adherance to a classical notion of aggression in similar studies might bias the initial question-asking stages of an investigation.
鉴于在互利共生的蚂蚁 - 植物关联研究中已成为普遍预期的一点，即蚂蚁具有明显的攻击性行为特征以发挥抗食草动物防御功能，对蚁栖胡椒属植物进行了重新研究。胡椒属植物为费氏蚁属蚂蚁居民提供食物和庇护所。这些蚂蚁体型小且“行动迟缓”，此前人们认为它们为植物获取养分，尽管它们的觅食活动可能仅限于植物表面，且大多数蚂蚁的食物是由植物自身产生的。一个替代假设是，费氏蚁属蚂蚁通过扰乱胡椒属植物叶片上处于卵期或早期幼虫期的食草动物来发挥抗食草动物防御功能，该假设通过以下推理思路进行了检验：（1）如果最嫩的幼叶更容易受到食草动物攻击，或者对植物更有价值，那么蚂蚁可能会优先“巡逻”这些叶子。在幼叶上发现的蚂蚁更多（[公式：见文本]=2.00只蚂蚁/叶），而在成熟叶上（[公式：见文本]=0.51只蚂蚁/叶）较少。（2）如果蚂蚁发挥抗食草动物防御功能，那么有蚂蚁栖息的植物上的食草动物侵害程度应低于没有蚂蚁的植物。对每株树苗的平均叶片被食草动物损害百分比的估计表明，对于平均高度相似（大概年龄也相似）的样本，没有蚂蚁栖息的植物受到的损害明显更大。对最新叶片的比较显示出随着蚂蚁活动增加损害减少的显著趋势。（3）如果蚂蚁在食草动物发育早期就对其进行攻击，那么用卵作为诱饵应该能证明这种活动。在30或60分钟的观察期内，幼叶和成熟叶上超过75%的所有卵诱饵被一只蚂蚁取走。在幼叶上发现诱饵的速度明显快于成熟叶。在超过一半的诱饵试验中，卵被带到叶边缘然后掉到地上，而不是被当作养分来源储存起来。这些数据表明，栖息在胡椒属植物上的费氏蚁属蚂蚁在植物防御食草动物方面很重要，并且在类似研究中坚持传统的攻击概念可能会使调查的初始提问阶段产生偏差。
