On the Nature of Individual Variation in Diapause Induction among the Progeny of Trichogramma telengai Sor. (Hymenoptera, Trichogrammatidae)

Abstract

In this communication, we analyze the variation in diapause incidence among isofemale substrains of the main laboratory strain of Trichogramma telengai Sor. (Hymenoptera, Trichogrammatidae) in order to clarify the nature of the previously discovered individual (intrastrain) variation in this trait. During the experiment, the maternal generation developed at a temperature of 20°C under a day length of either 12 or 18 h, and diapause in the progeny was induced by development at 14°C in darkness. In total, the experiment comprised eight replicates in which female diapause incidence was measured in 428 substrains in two consecutive generations. There was statistically significant individual (first-generation) and interfamilial (second-generation) variation in almost all of the replicates. However, the correlation between the diapause incidence values among the progeny of two consecutive generations of the same substrains was weak and largely nonsignificant. These results suggest that intrastrain variation in the percentage of diapausing progeny of T. telengai females is not primarily produced by genetic (hereditary) factors but is due to certain environmental (nonhereditary) effects.