McGregor Robert
Behavioural Ecology Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada.
Evolution. 1996 Aug;50(4):1579-1584. doi: 10.1111/j.1558-5646.1996.tb03930.x.
Direct measurements of phenotypic selection by parasitoids on quantitative traits in herbivorous insects have been rare. I analysed episodes of phenotypic selection on the timing of life-history events in a multivoltine leafmining moth, Phyllonorycter mespilella, and assessed the importance of hymenopterous parasitoids as selective influences. Phyllonorycter mespilella has two consecutive stages of larval development, the sap-feeding (SF) and tissue-feeding (TF) stages. Adult parasitoids host feed predominantly on SF larvae, and oviposit predominantly on TF larvae. Oviposition attack on TF larvae caused positive directional selection on the date of transition to the the TF stage (TF date) in the third generation of P. mespilella in one population in 1991. Overwinter mortality caused negative directional selection on TF date in the third generation in a second population in 1993. No directional or variance selection on TF date was detected in the second population in the second generation of 1993. Parasitoid females accepted SF larvae for oviposition more often in the fall generation than in summer generations in both populations. The relative frequencies of SF and TF larvae may alter the pattern of oviposition attack by parasitoids, and thus the form of phenotypic selection on TF date.
对寄生性天敌针对植食性昆虫数量性状进行的表型选择进行直接测量的情况较为罕见。我分析了多化性潜叶蛾Phyllonorycter mespilella生活史事件发生时间上的表型选择事件，并评估了膜翅目寄生性天敌作为选择影响因素的重要性。Phyllonorycter mespilella有两个连续的幼虫发育阶段，即吸食树液阶段（SF）和取食组织阶段（TF）。成年寄生性天敌主要以SF幼虫为寄主进行取食，主要在TF幼虫上产卵。1991年，在一个种群中，对TF幼虫的产卵攻击导致了第三代Phyllonorycter mespilella向TF阶段转变日期（TF日期）的正向定向选择。1993年，在第二个种群中，越冬死亡率导致了第三代TF日期的负向定向选择。在1993年第二代的第二个种群中，未检测到对TF日期的定向或方差选择。在两个种群中，寄生性天敌雌虫在秋季世代比夏季世代更常接受SF幼虫用于产卵。SF和TF幼虫的相对频率可能会改变寄生性天敌的产卵攻击模式，从而改变TF日期上的表型选择形式。
