Until now, with regard to the hobo system of hybrid
dysgenesis, natural populations of Drosophila
melanogaster have been investigated using only two criteria: at
the molecular level, the presence or
absence of XhoI fragments 2·6 kb long or smaller;
and/or at the genetic level, the ability to induce
gonadal dysgenesis sterility in crosses A (females of an E reference
strain crossed with males under
test) and A* (females under test crossed with males of an H
reference strain). Recently, analyses of
laboratory strains using these criteria as well as the mobilization of
two reporter genes, the male
recombination and the number of ‘TPE’ repeats in the
S region, revealed a lack of correlation
between the different dysgenic parameters themselves, and also
between these parameters and the
molecular characteristics of the strains. Thirteen current strains
derived from world populations
were therefore investigated with regard to all these dysgenic traits,
to determine discriminating
criteria providing a robust method of classifying natural populations
and deducing the dynamics of hobo elements in these populations. We show, as in laboratory
strains, a lack of correlation
between the parameters studied. Therefore, the significance of each of
them as well as the nature
of hobo hybrid dysgenesis are discussed, to propose an analysis
method of the hobo system
applicable to natural populations. According to the geographical
distribution of hobo activities in
world populations and to the variable polymorphism of the number of
‘TPE’ repeats, we propose
a new scenario for the invasion of D. melanogaster by hobo elements.
GENETIC AND BIOCHEMICAL BASIS OF ENZYME ACTIVITY VARIATION IN NATURAL POPULATIONS. I. ALCOHOL DEHYDROGENASE IN DROSOPHILA MELANOGASTER