西花蓟马的快速冷驯化及其生态学代价

Rapid cold hardening of Western flower thrips,Frankliniella occidentalis,and its ecological cost

西花蓟马是我国蔬菜、果树和观赏植物上的一种重要入侵害虫。该害虫通过取食寄主汁液和传播多种植物病毒造成危害,而后者危害造成的经济损失更大。温度是影响西花蓟马生长发育和繁殖的一个重要非生物因子,而该虫对温度的耐受性决定了它的越冬存活率和地理分布。为探明低温对西花蓟马的不利影响,研究了西花蓟马若虫和成虫的快速冷驯化对其存活、发育和繁殖的影响。结果表明,随着温度降低,西花蓟马若虫和成虫存活率逐渐下降,但若虫对低温更为敏感。当成虫和若虫暴露于-13℃和-13.5℃下2 h后,其存活率分别为25%和27%。根据识别温度定义,这两个温度分别被定义为若虫和成虫的识别温度。将西花蓟马成、若虫在0℃或5℃驯化2 h后,再置于各自识别温度下,其存活率都得到了明显提高,但雌雄成虫间的存活率并无差异;然而,在0℃下驯化2 h后,若虫和雌雄成虫的存活率得到了最大幅度的地提高,分别达46%、54%、49%。西花蓟马若虫经不同低温处理后,其发育历期、羽化后的成虫寿命、产卵时间与对照相比无显著差异,但产卵量显著降低;成虫经过低温处理后,其寿命,产卵量和产卵时间明显降低。研究结果支持昆虫快速冷驯化与其适合度之间存在平衡的假说;同时,也可为该虫的分布和治理研究提供相应的基础信息。

The western flower thrips （WFT）, Frankliniella occidentalis, is a key invasive pest of vegetables, fruits and ornamental crops in China. It can cause damage by direct feeding and transmitting plant viruses, such as tospovirus, and the latter often causes greater economic losses. Temperature is one of the most important abiotic factors that affect the development and reproduction of this pest. Geographical distribution and overwintering survival of the thrips mainly depend on its tolerance to low temperature in the winter. The present study examined the effects of rapid cold hardening at larval and adult stages on survival, development, and reproduction of F. occidentalis. Morality of both larvae and adults increased with the decrease of temperature, but the larvae were more sensitive to cold than adults. When larvae and adults of F. occidentalis were transferred from the normal rearing conditions at （26±1）℃, to cold temperatures at -13% （for larvae） or -13. 5% （for adults） for 2 h, survivorship rate was only 25% for larvae and 27% for the adults. These two temperatures could be defined as the discriminating temperatures for the two insect stages, respectively. Survival rates of the thrips that were pretreated at 0℃ or 5℃ for 2h before exposure to their discriminating temperatures increased significantly. The response of adult males and females was similar. Maximum increase in survivorships to the cold temperatures was achieved by pretreating larvae or adults at 0℃ for 2hs, which resulted in a survivorship rate of 46% , 54%, 49% for larvae, adult females and males, respectively. When cold exposures occurred at the larval stage, there were no differences in development time, longevity and reproduction duration of enclosed adults relative to the non-treated control. However the number of eggs laid of the adults derived from cold-treated larvae was significantly less than that of the non-treated thrips. When adult thrips were exposed to the cold temperatures, the longevity, fecundity and reproduction duration all decreased significantly compared to the non-cold treated control. Results of the current study support the hypothesis that a trade-off exists between the rapid cold hardening and fitness in insect. In addition, data generated from this study may also provide useful information in determination of potential distribution of the thrips and development of management strategies for this invasive pest.