Classical and augmentation biological control depend on
the successful laboratory rearing of natural enemies, but
rearing methods can affect the success and productivity
of a laboratory colony. One process that can occur
during rearing is the loss of genetic variability due to
inbreeding. The aim of this study was to examine the
influence of rearing methods with and without inbreeding
in
Mastrus ridens Horstmann, a hymenopteran parasitoid
specialist of the codling moth (
Cydia pomonella
[L.]),
on several fitness traits. Traits of females from mixed
and endogamous populations resulting from different
rearing methods were compared, as well as traits of
females from the same population subjected to sib-mating
or outbreeding. Longevity, parasitism, total fecundity,
and number of sons were similar for females in both
evaluations. The number of daughters was lower (1.9 ± 0.6
vs. 4.5 ± 0.5) and the offspring sex ratio was higher (0.81
± 0.04 vs. 0.48 ± 0.05 proportion of males) in females
from the endogamous population compared to females
of the mixed population, as well as in sib-mating females
compared to outbred females of the same population (0.5
± 0.3 vs. 5.8 ± 1.9 daughters and 0.94 ± 0.03 vs. 0.51 ±
0.10 sex ratio). These results show that rearing methods,
specifically inbreeding conditions, have an effect on
M.
ridens fitness; thus, successful outbred laboratory rearing
should be promoted.
