The opportunity for sexual selection and the evolution of non-responsiveness to pesticides, sterility inducers and contraceptives

Abstract

We illustrate a method for delaying and possibly eliminating the evolution of non-responsiveness to the treatments now used to control pest populations. Using simulations and estimates of the variance in relative fitness, i.e., the opportunity for selection, in a rat-like mammal, we show that the selection responsible for the evolution of non-responsiveness to pesticides and sterility-inducers, is similar in its action to sexual selection, and for this reason can be orders of magnitude stronger than that which exists for untreated populations. In contrast, we show that when contraceptives are used to reduce the fertility of a pest species, with non-responders embedded within such populations, the opportunity for selection favoring non-responsiveness is reduced to that which is expected by chance alone. In pest species with separate sexes, we show that efforts to control pest populations or to mitigate selection favoring non-responsiveness, are likely to be ineffective when members of one sex are sterilized or killed. We also show that while mating preferences can impede the rate at which resistance evolves, they are more likely to accelerate this process, arguing against the use of sterile male approaches for controlling pests. Our results suggest that contraceptives are more effective at controlling pest populations and slowing the evolution of non-responsiveness than treatments that cause sterilization or death in target species. Furthermore, our results indicate that contraceptives that work differentially on each sex will be most effective in mitigating selection favoring non-responders. Our results have significant implications for the development and application of treatments to manage pests, now and into the future.

A Systematic Review and Meta-Analysis of the Inhibitory Effects of Plant-Derived Sterilants on Rodent Population Abundance

“…In the 21st century, fertility control has become a humane, sustainable technology with few negative effects for controlling rodent damage and thus has attracted substantial attention. Knipling [ 34 ] first proposed making male rodents sexually sterile to control rodent damage. Davis [ 35 ] studied the application of chemical sterilants, such as triethylenemelamine, to control the population abundance of Rattus norvegicus .…”

“…In the 21st century, fertility control has become a humane, sustainable technology with few negative effects for controlling rodent damage and thus has attracted substantial attention. Knipling [34] first proposed making male rodents sexually sterile to control ro-Figure 7. Forest plot of the rodent organ coefficients.…”

The demographic consequences of fertility reduction in rats and voles

“…We emphasize that the goal of fertility control in general, and of our analysis, is not to extirpate rodent populations by reducing their population sizes to zero. This policy imposes the same intensity of selection that favors the evolution of resistance to rodenticide treatment (Shuster et al 2018). Instead, we illustrate that fertility control can reduce rodent populations to numbers at which these species are no longer recognized as pests.…”

“…Furthermore, in most applications, sterility is imposed upon such a large fraction of the population that only non-responsive individuals contribute to future generations. Thus, resistance to sterilants evolves for the same reasons that resistance evolves to rodenticides (Kirkpatrick 2007;Drury et al 2017;Magiafoglou et al 2003;Shuster et al 2018). Theoretical frameworks used to understand the effects of sterilization and other forms of fertility control on rat population growth have predicted that fertility management will be ineffective in controlling rat populations, particularly those undergoing expansion (Knipling and McGuire 1972;Hone 1992Hone , 2004).…”

“…We have shown elsewhere that the opportunity for selection (I = VW/W 2 , where VW=variance in fitness; W=mean fitness; Crow 1958;Shuster and Wade 2003) favoring resistance imposed by rodenticides and sterility inducers is among the most powerful evolutionary forces known (I > 1.0 × 10 5 ; Shuster et al 2018). We have also shown that, compared to how selection favors resistance to rodenticides and sterilants, the opportunity for selection favoring resistance to contraceptives, which reduce fertility rather than attempt to extirpate pest populations, is likely to be no greater than that expected by chance alone (I < 0.05; Shuster et al 2018). These results argue that in addition to providing a means for arresting rodent population growth, fertility reduction represents a sustainable, non-lethal method for rodent pest control.…”