Dispersal polymorphism in the diamondback moth, Plutella xyllostella grown on different host plants, and its ecological significance

众所周知，野生十字花科植物Rorippa indica和Lepidium virginicum可以作为小菜蛾（diamondback moth，小菜蛾）的寄主植物，但在成虫体型和繁殖力方面，它们不如栽培十字花科植物白菜更适合。对不同寄主植物上成虫的生活史、性状和飞行活性进行了研究。一般来说，生长在野生十字花科植物上的雌性成虫比生长在卷心菜上的雌性成虫繁殖能力更低，寿命更长。在野生十字花科植物上生长的成虫的飞行活动高于在卷心菜上生长的成虫。雄成虫比雌成虫飞得长。在同一寄主植物上饲养的成虫的繁殖力、寿命、飞行活性和形态计量特征与蛹重呈正相关。在不同寄主植物上生长的相同大小组雌蜂的繁殖力与飞行活动呈负相关，而在同一寄主植物上饲养的不同大小组雌蜂的繁殖力与飞行活动呈正相关。在籼稻上生长的成虫体内甘油的含量往往高于在白菜上生长的成虫。其他营养物质、糖原、总糖和游离氨基酸的含量，在籼稻上生长的成虫往往比在白菜上生长的成虫要低。这些事实表明，幼虫寄主植物影响了DBM中飞行燃料和产卵之间的营养分配。研究了4代DBM对野生寄主植物籼稻和白菜的适应能力的变化。在籼稻和小白菜两种驯化系中，籼稻系的发育期均短于小白菜系。籼稻系和白菜系的雌成虫繁殖力无显著差异。这一事实表明，黄花系的DBM已在一定程度上适应了黄花系。

The wild crucifers, Rorippa indica and Lepidium virginicum, are known to serve as host plants for the diamondback moth (DBM), Plutella xylostella, but they are less suitable than the preferred cultivated cruciferous plant, cabbage, in terms of adult body size and fecundity. The life history traits and flight activity of DBM adults grown on various host plnts were investigated. In general, female adults grown on the wild crucifers were less fecund and lived longer than those reared on cabbage. Flight activity was higher in adults grown on wild crucifers than in those reared on cabbage. Male adults flew longer than females. Fecundity, longevity, flight activity and morphometrical characters of adults were positively correlated with pupal weight in individuals reared on the same host plant. A negative relationship was found between fecundity and flight activity in females of the same size group grown on different host plants, but a positive one was observed in different sized females reared on the same host plant. The amounts of glycerides tended to be higher in teh adults grown on R.indica than in those grown on cabbage. The amounts of other nutrients, glycogen, total sugars and free amino acids tended to be lower in the adults grown on R.indica than in those grown on cabbage. These facts suggest that larval host plants influence nutrient allocation between flight fuel and egg production in the DBM.Changes in the ability of the DBM to habituate to wild host plants, R.indica and cabbage for four generetions were examined. For both habituated lines, R.indica and cabbage, the developmental period of R.indica line was shorter than that of cabbage line. The fecundity of female adults was not different between R.indica and cabbage lines. This fact suggests that the DBM of R.indica line have habituated in some degree to R.indica.