Resolution:
standard / ## Figure 1.
Dynamics and equilibrium conditions of density-dependent-limited populations under
RIDL/SIT control. We compared the effectiveness of SIT (blue line) and a late-acting lethal RIDL strategy
(thick red line) in a mathematical model of a continuous breeding Ae. aegypti population limited by density-dependent mortality (for details of the model see Methods).
The population is assumed to start at equilibrium carrying capacity, and will therefore
remain at the initial level if there is no intervention (black line). All releases
are assumed to be of males only; the input release ratio, I, is defined relative to the initial wild male population; this rate of release of
males then remains constant through time. In panels A and B, we plotted examples of
the variation over time, from the start of control, of the number of females in the
population relative to the initial number, for two different release ratios. The RIDL
insects are assumed to be homozygous for a construct lethal to males and females ("non-sex-specific")
after the density-dependent phase. For conventional SIT, mortality is assumed to be early
(at embryogenesis), before any density-dependent mortality operates. With a low release ratio (A), SIT can actually
increase the equilibrium size of the adult female population while RIDL can result
in eradication. With a sufficiently high release ratio (B), conventional SIT can control
the population, but the RIDL strategy is more effective. In panels C, D, E and F,
we plot the equilibrium number of female mosquitoes in the population, relative to
the initial numbers, following control with a given input ratio. The critical input
ratios required to achieve eradication are shown as broken lines for the conventional
SIT (blue) and RIDL systems (red). β represents the intensity of the density-dependence; P is the maximum per capita daily egg production rate corrected for density-independent
egg to adult survival (see Methods). Parameter values for β and P (indicated in the panels) represent the best-estimate ranges calculated by Dye for
a natural Ae. aegypti population [25]. In all cases, T = 27 days and δ = 0.12 per day; parameter values again taken from Dye [25].
Phuc |