Lack of Radioresistance in Plodia interpunctella (Lepidoptera: Phycitidae) Exposed to Sublethal Gamma Irradiation for 30 Generations
Populations of Plodia interpunctella receiving sublethal doses of irradiation (0.5, 1, 2, and 4 krad) each generation for 30 generations were checked for reproductive capacity and resistance to an acute dose of irradiation. Reproductive capacity was decreased by an ancestral history of irradiation, and the reduction was generally positively correlated with both the size of the dose per generation and the number of ancestral generations treated. Irradiation of selected populations with an acute dose revealed no increase. in tolerance, even after 30 generations. In general, the greater the amount of ancestral irradiations, the greater the sensitivity. (auth)
The negative exponential and Wiebull distributions were used to estimate stand survivorship curves for forested sites in the Porcupine River drainage of interior Alaska. The survivorship curve of Piceaglauca (Moench) Voss sites was best described by a Wiebull function, while both functions adequately described the Piceamariana (Mill.) Britton, Sterns & Poggenburg hardwood and all sites stand survivorship curve. Fire cycles calculated from the Wiebull distribution were 43, 113, 36, and 26 years for the entire study area, P. glauca, P. mariana, and hardwood sites, respectively. Fire frequencies estimated from a life table analysis were 48, 105, 43, and 30 years, respectively. The relationship between fire cycle and fire frequency calculations is discussed and various management implications are given.