Ohgushi Takayuki
Laboratory of Entomology, Faculty of Agriculture, Kyoto University, 606, Kyoto, Japan.
Oecologia. 1996 May;106(3):345-351. doi: 10.1007/BF00334562.
A reproductive tradeoff between current egg production and subsequent survival in a lady beetle, Epilachna niponica, a specialist herbivore on a thistle, Cirsium kagamontanum, was investigated at the two study sites, A and F. Survival of reproductive females decreased consistently from early May until mid-June, but apparently increased thereafter. In contrast, males showed a consistent decrease in survival throughout the reproductive season, without any sign of recovery. Dissection of ovaries of sampled females revealed that egg resorption increased late in the reproductive season, coincident with increased female survival. Reproductive females stopped oviposition immediately after a large flood in 1979 at site F. Two weeks after the habitat perturbation, females resumed oviposition in response to a flush of new leaves on damaged plants. Female survival sharply increased during the nonoviposition period, and declined when egg-laying resumed. Approximately 40% of long-lived reproductive females at site F survived up to the following reproductive season in the next year. Also, some of these long-lived females were observed ovipositing in the following reproductive season. The long-lived reproductive females which had previously invested in reproduction survived equally well as newly emerged females which had not reproduced in summer. These results suggest that there is a reproductive tradeoff between current egg production and subsequent survival. Egg resorption may be an adaptive ovipositional response to habitat perturbation such as flooding, which considerably reduces offspring fitness due to absolute shortage of food. Also, increased female survival accompanied by egg resorption enhances the likelihood of the future oviposition in the second reproductive season, thereby increasing a female's lifetime reproductive success.
在两个研究地点A和F，对日本方头甲（Epilachna niponica）——一种以蓟（Cirsium kagamontanum）为食的专食性食草动物——当前产卵量与后续生存之间的生殖权衡进行了研究。生殖期雌虫的存活率从5月初到6月中旬持续下降，但此后明显上升。相比之下，雄虫在整个生殖季节的存活率持续下降，没有任何恢复的迹象。对采样雌虫卵巢的解剖显示，在生殖季节后期卵吸收增加，这与雌虫存活率的增加同时出现。1979年F地点发生大洪水后，生殖期雌虫立即停止产卵。栖息地受到干扰两周后，雌虫因受损植物上新叶的萌发而恢复产卵。雌虫在非产卵期存活率急剧上升，而在恢复产卵时下降。F地点约40%的长寿生殖期雌虫存活到次年的下一个生殖季节。此外，还观察到其中一些长寿雌虫在下一个生殖季节产卵。之前已投入繁殖的长寿生殖期雌虫与夏季未繁殖的新羽化雌虫存活情况相当。这些结果表明，当前产卵量与后续生存之间存在生殖权衡。卵吸收可能是对诸如洪水等栖息地干扰的一种适应性产卵反应，洪水会因食物绝对短缺而大幅降低后代适合度。此外，伴随卵吸收而来的雌虫存活率增加提高了在第二个生殖季节未来产卵的可能性，从而增加了雌虫一生的生殖成功率。
