A hybrid dysgenesis syndrome in Drosophila virilis
is associated with the mobilization of at least
four unrelated transposable elements designated Helena, Paris,
Penelope and Ulysses. We carried
out 42 crosses between eight strains differing in transposable element
copy number in order to
assess their contributions to hybrid dysgenesis. Linear regression and
stepwise regression analysis
was performed to estimate the correlation between the difference in euchromatic
transposable
element number between the parental flies of different strains involved
in the crosses and the
percentage, in the progeny of these crosses, of males with atrophic
gonads. Male gonadal atrophy
is a typical manifestation of the D. virilis hybrid dysgenesis
syndrome. About half the variability in
the level of male gonadal atrophy can be attributed to
Penelope and Paris/Helena. Other factors
also seem to play a significant role in hybrid dysgenesis in D. virilis,
including maternally
transmitted host factors and/or uncontrolled environmental variation.
In the course of this work a
novel transposable element named Telemac was found. Telemac
is also mobilized in hybrid
dysgenesis but does not appear to play a major causative role.