隔離寄主時間對綠豆象（Callosobruchus chinensis）及四紋豆象（C. maculatus）雌蟲產卵與壽命之影響

Effect of host deprivation period on fecundity and longevity of the seed beetles Callosobruchus chinensis and C. maculatus

綠豆象（Callosobruchus chinensis（L.））及四紋豆象（C. maculatus（F.））屬於鞘翅目豆象科（Bruchidae）是重要的倉儲害蟲，藉由食物資源變化之處理如寄主資源不足或無寄主資源等，可探討兩種豆象在面對寄主隔離情況之生活史策略反應，即是否能彈性地利用有限資源，以作為評估兩種豆象種間競爭過程之參考。本試驗的目的為探討隔離寄主時間的長短，對兩種豆象在繁殖及壽命特性變化之影響。經隔離寄主2至8日處理下，綠豆象及四紋豆象雌蟲之產卵數均隨隔離寄主時間增加而顯著降低，而綠豆象產卵數之降低較四紋豆象為大。分析不同隔離寄主時間下，豆象雌蟲每日之產卵數變化，結果發現當綠豆象隔離日數較少時（2日），其再接觸寄主之第一日產卵數與無隔離寄主處理雌蟲無顯著差異，但是當隔離寄主時間較長時（4及8日），其第一日產卵數則顯著降低；四紋豆象則隨隔離寄主時間延長其第一日產卵數反而顯著增加，惟當隔離寄主時間達8日時，其第一日產卵數與無隔離處理雌蟲無差異。而比較產卵第一日之卵平均擁擠度，顯示兩種豆象雌蟲經歷過隔離寄主後，其產卵行為皆產生改變，亦即對已產卵寄主之接受機率增加。卵孵化率之結果顯示，隔離寄主時間達8日時，兩種四紋豆象雌蟲卵孵化率皆顯著下降，因此隔離寄主時間較長時，對綠豆象及四紋豆象雌蟲卵之品質有不良影響。此外，隨隔離寄主時間增加，綠豆象及四紋豆象壽命均顯著延長，因此進一步分析證實其產卵數與壽命之間有權衡的現象。顯示綠豆象及四紋豆象皆能因應無寄主資源而調節其產卵數與壽命之間的能量分配。惟綠豆象其減少產卵數所餘之能量對壽命之增加程度較四紋豆象為小。

"The effects of host deprivation on the life history strategy of the seed beetles, Callosobruchus chinensis (L.) and C. maculatus (F.), were explored in this study. The results may provide information for examining interspecific competition of these 2 seed beetles. After depriving beetles of hosts for 2, 4, or 8 days, females of both species would reduce fecundity and channeled their energy into sustaining their lives. However, the effect of deprivation on fecundity reduction in C. chinensis was more serious than that in C. maculatus. In addition, we found that the effect of deprivation on the rate of egg reproduction differed for these 2 seed beetles. It appeared that the rate of reproduction in C. chinensis was reduced with increasing duration of host deprivation, whereas in C. maculatus, it increased with increasing duration of host deprivation. After being deprived of hosts, females of both species distributed their eggs less uniformly among hosts. Therefore, the oviposition preference, i.e., acceptability of hosts with eggs by these 2 seed beetles was changed by host deprivation. The hatchability of eggs laid by these 2 seed beetles significantly decreased if females were deprived of hosts for 8 days. Thus, increased deprivation time appeared to reduce egg quality. Our results also showed that longevity was negatively correlated with the fecundity of these 2 seed beetles, and therefore trade-offs between fecundity and longevity were exhibited by these 2 seed beetles. The importance of life history strategies on competition between these 2 seed beetles is also discussed."