Desouhant E, Debouzie D, Ploye H, Menu F
UMR CNRS 5558 "Biométrie et Biologie Evolutive", Univ. C. Bernard, Lyon I, 43, bd du 11 novembre 1918, F-69622 Villeurbanne Cedex, France e-mail:
Oecologia. 2000 Mar;122(4):493-499. doi: 10.1007/s004420050971.
We test the adaptive value of clutch size observed in a natural population of the chestnut weevil Curculio elephas. Clutch size is defined as the number of immatures per infested chestnut. In natural conditions, clutch size averages 1.7 eggs. By manipulating clutch size in the field, we demonstrate that deviations from the theoretical "Lack clutch size", estimated as eight immatures, are mainly due to proximate and delayed effects of clutch size on offspring performance. We show the existence of a trade-off between clutch size and larval weight. The latter, a key life-history trait, is highly correlated with fitness because it is a strong determinant of larval survival and potential fecundity of offspring females. The fitness of different potential oviposition strategies characterized by their clutch sizes, ranging from one to nine immatures, was calculated from field- estimated parameters. Chestnut weevil females obtain an evolutionary advantage by laying their eggs singly, since, for instance, fitness of single-egg clutches exceeds fitness of two-egg clutches and four-egg clutches by 8.0% and 15.1% respectively.
我们对在栗实象甲Curculio elephas自然种群中观察到的窝卵数的适应值进行了测试。窝卵数定义为每颗受侵染栗子中的未成熟个体数量。在自然条件下，窝卵数平均为1.7枚卵。通过在野外操纵窝卵数，我们证明，与理论上估计为8个未成熟个体的“拉克窝卵数”的偏差，主要是由于窝卵数对后代表现的直接和延迟影响。我们表明窝卵数与幼虫体重之间存在权衡。后者是一个关键的生活史特征，与适合度高度相关，因为它是幼虫存活和后代雌性潜在繁殖力的一个重要决定因素。根据野外估计的参数，计算了以窝卵数从1到9个未成熟个体为特征的不同潜在产卵策略的适合度。栗实象甲雌性通过单粒产卵获得进化优势，例如，单卵窝的适合度分别比双卵窝和四卵窝的适合度高出8.0%和15.1%。
