keystone in biodiversity : indirect interactions

(1)双因素方差分析发现，3个性能性状均存在显著的草食效应和宿主-草食交互作用。在发育过程中，发现了明显的宿主效应。(2)利用性竞争、叶片脱落和落卵等因素导致的适合度降低具有明显的密度依赖性。然而，高密度环境下的适应度下降是由于天敌的攻击造成的。野外常见的窝数显示出最高的适合度，聚集产卵增加密度不会降低适合度。因此，叶螨的产卵策略几乎是自适应的。(3)锯蝇密度和存活率与植物种群年龄呈负相关。卷叶蛾和寄生蜂的密度随种群年龄的增长而增加，但象鼻虫的密度没有增加。青壮年人群的寄生率较高，老年人群的死亡率较高。(4)与未损伤苗相比，损伤苗的新芽数量更多，新芽长度更长。这些结果表明，代偿性枝条生长是由于喷虫产卵导致枝条顶端区域死亡造成的。(5)不同无性系间叶片挥发物含量差异较大，但其形态和比例均具有种特异性。不同树种间主要挥发物的含量差异明显，粗叶参的挥发物含量是全叶参的20倍。(6)沙沙林叶上的成虫对沙沙林叶提取物处理过的琼脂盘的偏好高于对整叶提取物处理过的琼脂盘。另一方面，采食整片柳甲的柳甲对分别用sachalinensis和S.integra处理的琼脂盘均有接受。在两个选择测试中，喂食比例非常相似。该菌至少有两种化学种类（atsubetu型和shinkawa型）。柳甲虫在新川型整条蝽上可以繁殖，但成年雌虫在采食忠别型整条蝽后不能产卵。少

(1) Two-factor ANOVAs detected significant herbivore effects and host-herbivore interactions in the three performance characters. In developmental time, a significant host effect was detected. These results indicate geographical difference not only in genetic architecture of P.versicolora but also in quality of S.integra.(2) The experiments demonstrated clearly density-dependent reduction in fitness through exploitative competition, leaf abscission, and egg dropping. However, the decreased fitness in high density was caused by natural enemy attacking. Common clutch size in the field shows the highest fitness, and increased density by aggregated oviposition would not decrease fitness. Hence, the oviposition strategy of the leaf miner would be almost adaptive.(3) Sawfly density and survival rate were negatively correlated with plant population age. Density of leaf-rolling moth and parasitoids increased with population age, but not for weevils. Parasitism was high in young population, whi … More le weevil-caused mortality was high in old population.(4) The number of new buds was greater and the length of new growing shoots was longer on damaged shoots than on non-damaged shoots. These results show that the compensatory shoot growth was caused by the death of the apical regions of the shoots due to spittlebug oviposition.(5) Both of patterns and proportions of leaf volatiles were species specific, although there were a wide variety in amount of each substance among clones. Difference in total amount of main volatiles between species was apparent : S.eriocarpa leaf included twenty times as much as in S.integra leaf.(6) Adult beetles on S.sachalinensis leaves preferred the agar disk treated with S.sachalinensis leaf extract to that treated with S.integra leaf extract. On the other hand, willow beetles fed on S.integra accepted both agar disks treated respectively with S.sachalinensis and S.integra. In both choice tests, the feeding ratio was quite similar to each other. There are at least two chemical species in S.integra (Atsubetsu-type and Shinkawa-type). Willow beetle could renew the generation on Shinkawa-type S.integra, but adult females could not oviposit when they were fed on Atsubetsu-type S.integra. Less