马尾松毛虫高海拔种群发生对光周期的响应:基于年龄-时期、两性生命表分析

Responses of a high altitude population of Dendrolimus punctutas to different photoperiods

马尾松毛虫Dendrolimus punctatus Walker是南方林业重大害虫,目前对其在高海拔区(>700 m)的发生特点仍不清楚。本研究从湖南绥宁(26.35°N,110.09°E)高海拔区采虫,放在5个光周期处理下饲养,以年龄-时期、两性生命表法计算种群参数,揭示光周期对该种群发生的影响。结果显示:L∶D=15.5∶8.5(15.5 h)和L∶D=14.5∶9.5(14.5 h)光周期处理组种群发生正常,而L∶D=11.5∶12.5(11.5 h)、L∶D=12.5∶11.5(12.5 h)和L∶D=13.5∶10.5(13.5 h)光周期处理组未观察到成虫发生。15.5 h组内禀增长率(r)为0.057 d-1,净生殖力(R0)为55.73粒,单雌产卵力(fecundity)为241.5粒,平均世代时间T为71.05 d,14.5 h组r为0.018 d-1,R0为6.29粒,显著低于15.5 h组。该种群在14.5 h光周期处理下表现出分散繁殖行为,即出现两个繁殖期,时差1个月左右。与15.5 h处理组相比,14.5 h处理组成虫寿命显著缩短。该研究表明:马尾松毛虫高海拔种群对光周期变化响应强烈,而湖南绥宁光周期在7月底就开始变短,当地马尾松毛虫在这种光周期诱导下较早进入滞育发育,因而种群年发生仅一代。

Dendrolimus punctutas Walker is a key forest-pest in South China, its population occurrence at highlands （〉700m） is still unknown. This study took samples of D. punctutas at the highland of Suining （26.35°N, 110.09°E）. These samples were treated by five successive photoperiods in laboratory, aiming to investigate the influence of photoperiod on the population parameters, which were computed by the method of age-stage, two-sex life tables. Results showed that the population occurrence finished completely at L：D = 15.5：8.5（15.5h） and L：D = 14.5：9.5（14.5h）, but partly at L：D = 11.5：12.5（11.5h）, L：D = 12.5：11.5（12.5h） and L：D = 13.5：10.5（13.5h）. The population parameters were counted as 0.057d-1 of intrinsic rate of increase（r）, 55.73 of net reproductive rate （R0）, 241.5/female of fecundity and 71.05d of mean generation time （T） at 15.5h, and the r and R0 were significantly higher than 0.018 d-1 and 6.29 at 14.5h. The dispersive breeding behavior was observed at 14.5h because reproduction distributed at two separate times, with the second time lagging almost one month. Adults at 14.5h showed a shorter longevity compared with those at 15.5h. It suggested that the response to photoperiod change was intensified in the highland population, and D. punctutas was early induced into diapause by the decrease of photoperiod since the end of July in Suining, thus it could be produced just one generation there annually.