高温对二化螟实验种群生长、存活和繁殖的影响

Effect of high temperature on the growth, survival and reproduction of a laboratory population of the rice stem borer Chilo suppressalis Walker

以2 7℃和30℃恒温为对照,研究了平均温度在2 7～2 9.2℃内的5种变温条件下(每天2 0 h的适温2 7℃和12 :0 0～16 :0 0的高温处理,分别为日最高气温2 7℃、30℃、33℃、36℃、4 0℃)二化螟实验种群的发育历期、存活率和繁殖力的影响,组建了特定年龄生命表和繁殖力生命表。结果表明高温可导致二化螟种群的发育速率延缓、存活率和生殖力下降,主要表现在幼虫历期随日最高温度的升高而延长,36℃时延至12 d以上;在日最高气温高于33℃时,其存活率从2 7℃时的30 .3%降至36℃时的13.1%和4 0℃时的5 .5 % ,繁殖力也从30℃时每雌产卵量14 8.7粒减至36℃时的70 .5粒。因此。

The influence of high temperature on the growth, survival and reproduction of a laboratory population of the rice stem borer (RSB), Chilo suppressalis, was studied by constructing age-specific life tables and fertility life tables under two constant temperatures (27°C and 30°C) and under fluctuating temperature regimes (20h at 27°C + 4h at 30°C, 20h at 27°C + 4h at 33°C, 20h at 27°C+4h at 36°C, or 20h at 27°C+4h at 40°C), in which the daily maximum temperature (Tmax) occurred between 12:00～16:00. The results indicated that high temperature could affect the survival and duration of larval development of RSB. The mean developmental period of the larvae exposed to a Tmax of 33°C was longer than the developmental periods under constant temperature, and the developmental period was prolonged by approximately two weeks when the Tmax was raised to 36°C. The duration of the other developmental stages of RSB did not show significant changes under high temperature. The survival ratio of larvae decreased acutely when Tmax was greater than 33°C, for example, from 30.3% at 27°C to 13.1% at 36°C and 5.5% at 40°C. The survival of other development stages also decreased significantly as Tmax increased to 36°C. The highest fecundity, 148.7 eggs per female, occurred at a Tmax of 30°C, but decreased to 70.5 eggs per female when Tmax increased to 36°C. Other life table parameters, the net reproductive rate R_0, the intrinsic capacity for increase r_m, finite rate of increase λ, and population growth index I, dropped rapidly as Tmax reached 36°C, while the mean length of a generation T was delayed as Tmax increased above 33°C. There were no significant differences in pupal weights under different Tmax levels. As compared with the fluctuating temperatures, there were no significant differences in growth, survival and fecundity between insects reared at the two constant temperature treatments of 27°C and 30°C. This experiment demonstrated that the larval stage was the stage most sensitive to daily maximum temperature. High temperatures will affect the survival and fecundity of RSB significantly. Therefore, abnormally high temperatures during summer will probably be an important factor determining the abundance of field populations of RSB. It may be assumed that the population density of RSB will decline during a very hot summer, and the emergence period of the moth will be postponed if the days of Tmax >35℃ are higher than normal.