The influence of irradiation on the behaviour and reproduction success of eight toothed bark beetle Ips typographus (Coleoptera: Scolytidae)

Abstract

Irradiation experiments on Ips typographus (L., 1758) with doses of 15 and 30 Gy (cobalt 60) were conducted in 2006. The effect of irradiation on the mating behaviour and reproduction success of the bark beetle has been evaluated in rearing experiments in the laboratory. The effect of treatment on basic rearing parameters - (a) galleries per log, (b) mating chambers per log, (c) galleries with mother tunnels, (d) galleries with larvae tunnels, (e) mother tunnels - was not statistically significant - (a) F = 0.609, d.f. = 4, P = 0.560; (b) F = 1.883, d.f. = 4, P = 0.194; (c) F = 1.322, d.f. = 4, P = 0.303; (d) F = 0.373, d.f. = 4, P = 0.697; (e) F = 0.519, d.f. = 4, P = 0.608, ANOVA. The comparison of detailed rearing parameters showed statistically significant differences in the size of the mating chamber only, when both irradiated variants produced a larger mating chamber than did the control beetles (F = 5.113, d.f. = 4, P = 0.025, ANOVA). Irradiation changed the behaviour of males, so that they moved significantly faster than males in control (n = 18, P = 0.001, t-test), and 15 Gy irradiated males were significantly more successful in competition for females than 30 Gy irradiated males (F = 8.067, d.f. = 6, P = 0.015, ANOVA). In contrast, the number of eggs produced by females was significantly lower in the 15 Gy (F = 5.13, d.f. = 17, P= 0.029, ANOVA) and 30 Gy (F = 5.292, d.f. = 17, P = 0.028, ANOVA) irradiated variants as compared to the control and, the number of hatched eggs was significantly higher in the control group than in the 15 Gy (F = 5.415, d.f. = 17, P = 0.025, ANOVA) and 30 Gy (F = 6.916, d.f. = 17, P = 0.014, ANOVA) variants. The results are discussed below.