Effects of cadmium on natural selection in gypsy moth (Lymantria dispar L.)

Abstract

Natural selection has significant effect on phenotypic changes in organisms exposed to chronic environmental stress induced by pollutants such as cadmium. The adaptation to such a stress comes as a direct result of natural selection in traits that will induce the evolution of tolerance to stressful environment both directly and indirectly. A statistic method was used in this experiment to determine the standard linear selection gradients (β’) and standard linear selection differentials (i’) used to estimate the intensity of the natural selection to certain traits of the adaptive values (LD – larval development; PM – pupae mass; PD – pupae development) in control group (C) and treatments ((T1 – 10 μg/g Cd; T2 – 30 μg/g Cd; iT3 – 50 μg/g Cd) where adults lifespan (AL) was considered to be the measure of the adaptive value. Significant negative selection gradients and differencials in males to LD in group T3 were determined in our experiment, as well as positive selection gradients and differentials in females to PM in groups C, T1 and T2. Females showed significant selection gradients and differentials to PM in grpoups C, T1 and T2 while the same occured with males from group C. Positive selection gradients and differencials to PD were determined in females from group T1 and males from groups C and T2. When exposed to stressful enviroments, larger females and males with shorter larval and pupal development seem to be favoured by natural selection.