壳斗科三种植物种子大小对昆虫寄生及种子存活率的影响

Effects of seed size on the survival of insect infested acorns in three oak species

关键词:  最优觅食理论  种子进化  种子萌发  种子足余策略  种子体积

Key words:  optimal foraging theory  seed evolution  seed germination  seed satiation strategy  seed size

摘要:

种子内的寄生昆虫可以严重影响种子的发育、损害种子活力。种子足余策略理论认为大种子有利于抵御和适应昆虫寄生取食，但动物最优觅食理论推测，大种子更易遭受昆虫寄生。为对这两种对立观点进行验证，本实验以青冈、苦槠和麻栎各2个种群的种子为材料，对昆虫寄生与完好种子间的体积和萌发率进行比较，并对寄生种子萌发率与种子体积的关系进行了分析。结果显示：(1)在6个种群的种子中，只有松阳麻栎和青冈种群的寄生种子体积大于完好种子，其余4个种群的寄生种子体积小于完好种子，但这种差异不显著；(2)所有寄生种子的整体萌发率(18%)显著低于完好种子(45.66%)(P＜0.001)，在不同种群内，寄生种子的萌发率也分别显著低于完好种子。(3)比较同种植物体积差异显著的寄生种子的萌发率发现，大种子总比小种子具有更高的萌发率，但差异不显著；在不同植物的寄生种子间比较时，体积最大的麻栎种子萌发率显著高于体积较小的青冈和苦槠种子。研究结果表明，象虫在种子上产卵时对大种子没有选择偏好，在昆虫寄生取食严重损害种子活力的压力下，大种子比小种子具有更强的耐受力。

Abstract:

Endogenous parasitizing insects greatly affect the development and survival of seeds. Seed satiation hypothesis propose that large seeds always survive better from insect infestation than small seeds，but animal optimal foraging theory suggests that large seeds may be infested by insect at a higher rate. Our objective was to test which one of the two conflicting hypotheses was actually in conformity with the seed adaptive strategy against insect parasitism in three oak species. Seeds of three oak species，Quercus glauca，Castanopsis sclerophylla and Q.acutissima were collected as study materials from Hangzhou city and Songyang county of Zhejiang，an eastern province of China. The size and germination rate of infested and sound seeds were studied for each species，and the relationship between germination rates and seed size of infested and non infested seeds were examined within species and between species. The results showed that:(i)the sizes of infested seeds of Q.acutissima and Q.glauca were insignificantly larger than those of sound seeds in populations from Songyang，but were insignificantly smaller in other 4 populations；(ii)germination rate of infested seeds was significantly lower than that of sound seeds in each population of the three species；(iii)for infested seeds of each oak species，large sized seeds always had a higher germination rate than small sized seeds，but the difference in germination rate was not statistically significant. Infested seeds of Q.acutissima，the species with largest seed，had a significant higher germination rate than the other two species. The results suggested that the weevils do not have a preferences to oviposit on large seed，but large seeds might be more tolerant to insect parasitism.