Simulating dynamic insecticide selection pressures for resistance management in mosquitoes assuming polygenic resistance
Fig 5
Compartmental diagram of truncation selection process for a single generation.
The “polytruncate” model implements truncation selection, and determines which equations are used to calculate each stage of the selection process. Note this process is calculated separately for males and females. Panel 1. The mosquito population emerges, with a PRS that is Normally distributed with mean (black line) and standard deviation
. At emergence there are a total of
individuals. Panel 2. A proportion (males:
and females:
) avoids the insecticide and insecticide selection; the mean is therefore unchanged at
, there will be
of these individuals (Equation 4d). Panel 3. A proportion do encounter the insecticide (males:
and females:
) (Equation 5d). Panel 4. These individuals are selected by truncation selection (Equation 5c). Individuals with a PRS less than the defined threshold (red line) are killed (red area). Individuals with a PRS above the threshold survive (blue area). Panel 5. Only the most resistant individuals in the population will have survived the insecticide encounter, these individuals have a mean of
(purple line) (Equation 5c), and there are
of these individuals (Equation 5d). Panel 6. The unexposed group (Panel 2) and the exposed survivors (Panel 5) form the final breeding parental population. They have a mean of
(orange line) (Equation 4b), which would be expected to be higher than the original population mean (black line). The insecticide selection differential is the difference between the orange and black lines (Equation 3b).