Aj. Lymbery et Ir. Dadour, Genetic structure of the Bovicola ovis (Mallophaga : Trichodectidae) in southwestern Australia, ENV ENTOMOL, 28(4), 1999, pp. 675-680
The sheep biting louse, Bovicola ovis (Schrank), is an economically importa
nt, worldwide ectoparasite of sheep. In Australia, up to 30% of sheep flock
s are infested with lice. The usual method of control has been synthetic py
rethroids applied as pour-on along the back of the sheep, but treatment fai
lures have become widespread since 1985 because of the development of resis
tance. We used allozyme markers to study the distribution of genetic variat
ion within and among populations of lice on different farms in Western Aust
ralia. Genetic variation within populations was similar to previously repor
ted values for other ectoparasitic arthropods. Heterozygote deficiencies we
re found at 1 locus ina number of population acid another 2 loci in 1 other
population. However, another variable locus conformed to Hardy-Weinberg eq
uilibrium and there was little evidence of extensive linkage disequilibrium
between loci, Further studies are necessary to establish the breeding syst
em. Genetic differences among populations were not related to geographic se
paration, which is consistent with an island model of population structure.
A small but significant proportion (2.8%) of the total genetic variation w
as distributed among populations' equivalent under the island model to a ge
ne flow of 8.7 individuals exchanged per generation. The implications of th
is result are discussed in terms of controlling and managing synthetic pyre
throid resistance in sheep biting lice.