关键词: 槲栎, 橡子, 象甲, 超寄生, 幼虫适合度

Abstract: Acorns of oaks are usually attacked by weevils. Although the interaction between acorns and weevils has been well studied, how acorns affect the fitness of weevil larvae remains unclear. In this study, we attempted to investigate the evolutionary adaptation of weevils to the development of acorns through carefully investigating the seed fall processes and the characteristics of larval emergence from the trapped acorns of the Oriental white oak, Quercus aliena. Our results indicated that seed crop of Q. aliena was 51.92 ± 29.26 nuts/m² with an infestation rate estimated of 42.4% in 2009. The infested acorns were much larger than the sound ones. About 65% of the infested acorns were superparasitized by weevil larvae. Weevil larvae emerged earlier were much larger than those exited later from infested acorns after seed fall. Early emerged weevil larvae were much larger than those coming out later from the same individual superparasitized acorn. Weevil larvae parasitized in the early abscised acorns were smaller than those in later abscised ones. Our results demonstrated that dry weight per weevil larva was decreased significantly with the increase in the number of weevil larvae in single acorn. The number of weevil larvae was closely and positively correlated with length and maximum width of acorns, respectively. Although the fitness of weevil larvae was reduced in the superparasitized acorns, a preference of female weevil for larger acorns to oviposition may counter this disadvantage. Our results may suggest that smaller acorns may benefit from superparasitization because large acorns attract female weevils to oviposit more eggs.

Key words: Quercus aliena, acorn, weevil, superparasitization, larval fitness