Data from: Development time and host-parasitoid stability: An experimental test

The duration of specific life stages and relative lengths of the predator
and prey life cycles can, in theory, exert strong influences on population
dynamics and may be important considerations in managing pest outbreaks.
However, rigorous experimental tests of this theory do not exist. We
conducted a microcosm experiment using the cowpea weevil (Callosobruchus
maculatus) and its parasitoid (Anisopteromalus calandrae) to assess how a
60% increase (long-duration treatment) or 60% decrease (short-duration
treatment) in the invulnerable (late larval to mid pupal) host stage
affected host-parasitoid population dynamics. We predicted that stability
is most likely for microcosms in the short-duration treatment, whereas
generation cycles should occur for the long-duration and control
treatments, with a longer period in the long-duration treatment. Our
results largely support these predictions. In the control treatment,
persistent oscillations occurred with a period of about one generation,
consistent with theory. The long-duration treatment produced cycles
similar in period and strength to the control, rather than predicted
longer period ones. As expected, cycles disappeared in the short-duration
treatment, and host densities were suppressed by 41-49% relative to the
other treatments. Variability in host densities in the short-duration
treatment was high, likely a consequence of demographic stochasticity in
small populations, whereas variability in parasitoid densities was 24-27%
lower than in the other treatments. Complementary simulation models that
closely matched the biological details and protocols used in the
experiment reproduced the observed dynamics in the short-duration and
control treatments. The oscillatory period observed in the long-duration
treatment was also replicated when stronger, scramble-type competition in
the weevil attack process was incorporated into the model. We conclude
that age structure and development time are critical determinants of
host-parasitoid population dynamics and should be explicitly considered in
the selection of biological control agents and in evaluations of program
success or failure.