Intraspecific differentiation in gradology and ecology of Pityogenes chalcographus L. (Col., Scolytidae) in view to interpopular crossing
1986
Klipstein, E.-L. (Goettingen Univ. (Germany, F.R.). Inst. fuer Forstzoologie)
German. Four regionally different strains and six F1 interpopular crosses of Pityogenes chalcographus were used for infestation and starvation experiments. In the infestation experiment beetles were placed for three days on vital Norway spruce and the amount of nuptial chambers were recorded. During the viability experiment the insects were kept under a daily varying temperature for 16h at 20 degrees C and for 8h at 10 degrees C. The rel. humidity was set at 93 per cent, 77 per cent and 57 per cent. The infestation potential differs in the susceptibility of host trees and within the populations. Especially the F1 crosses provide an enhanced attack and potential of injury which are to be considered a case of heterosis. Because of the irregular host-tree preference in some populations it is assumed that there is a highly specific interaction in feeding stimulation. The effect of heterosis is also present in starvation experiments, but it seems to be only restricted to an optimal survival range. It is emphasized that genetic factors play a remarkable role in the interactions between bark beetles and host trees as well as in population dynamics
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