Ar. Kraaijeveld et al., GEOGRAPHICAL VARIATION IN HABITAT CHOICE AND HOST SUITABILITY IN THE PARASITOID ASOBARA-RUFESCENS, Entomologia experimentalis et applicata, 72(2), 1994, pp. 109-114
In the Netherlands, Asobara rufescens (Forster) (Hymenoptera: Braconid
ae) is a parasitoid of drosophilid larvae in decaying plant material.
In several places in the Mediterranean, parasitoids looking very simil
ar to A. rufescens were collected on fermenting substrates a hybridiza
tion experiment showed that the parasitoids were indeed A rufescens. I
n an olfactometer Portuguese A. rufescens do not have a preference for
either the odour of yeast or decaying leaves, while their Dutch consp
ecifics prefer the odour of decaying leaves. The survival probability
of Portuguese A. rufescens in Drosophila melanogaster Meigen (Diptera:
Drosophilidae), a species typical for fermenting substrates, is much
higher than the survival probability of Dutch A. rufescens in this hos
t species.It is hypothesized that decaying plant material may be unsui
table for drosophilid larvae during part of the year in the Mediterran
ean, forcing A. rufescens there to broaden its microhabitat choice. Th
e use of fermenting substrates brings A. rufescens in contact with its
sibling A. tabida Nees, a species typical for fermenting substrates i
n most of Europe. Portuguese A. rufescens appear to be genetically iso
lated from A. tabida. In the Netherlands, where the two species occupy
different microhabitats, there is only a premating barrier.