Potential evolutionary rates of climate-sensitive traits
After identifying the climate factors and mosquito traits that limit population persistence, we can now compare their rates of change to predict whether populations can adapt apace with environmental change. To do so, we turn to evolutionary rescue models, which estimate the maximum rate of evolutionary change (i.e., adaptive genetic turnover) of a population and compare it to the projected rate of environmental change. Populations can persist only when their maximum sustainable evolutionary rate exceeds the required rate of evolution dictated by the environment (Bell and Gonzalez 2009, Hoffmann and Sgrò 2011, Gomulkiewicz and Shaw 2013, Gonzalez et al. 2013, Carlson et al. 2014, Bell 2017). Evolutionary rescue models explicitly model demographic rates and assume that populations are comprised of different genotypes with different reproductive advantages. As these models track population responses to sustained, directional environmental change, they are well-suited to estimating the potential for thermal adaptation in response to climate warming (Huey and Kingsolver 1993, Bürger and Lynch 1995, Chevin et al. 2010, Bay et al. 2017, Cotto et al. 2017, Diniz‐Filho et al. 2019), and have provided valuable estimates of climate adaptation potential across a range of taxa (Gienapp et al. 2013, Cotto et al. 2017, Diniz‐Filho et al. 2019). Even with incomplete or imprecise knowledge of all parameters, these models can place bounds on the climate response space to indicate where adaptation is highly unlikely and to inform future data collection efforts.
Here, we consider the analytic, quantitative-genetic evolutionary rescue model described by Chevin et al. (2010). This model estimates population adaptive potential under climate warming using (Box 1): 1) the maximum population growth rate under optimal conditions, 2) the population generation time, 3) the phenotypic variance in the trait of interest, 4) the strength of selection imposed by temperature change, 5) the trait heritability, 6) the degree of phenotypic plasticity in thermal tolerance, 7) how the trait optimum changes with temperature (i.e., environmental sensitivity of selection), and 8) the expected rate of temperature change during the time period. Although the simplicity of this analytic evolutionary rescue model may constrain the accuracy of its projections, it illustrates the basic factors likely to affect population persistence, which we consider to be the minimum information needed to make initial predictions (see Supporting Information Appendix A for additional unmodeled factors and the Discussion for methods to incorporate additional complexity). We present the main findings below, including information from the closely related model organismDrosophila when little information is available for mosquitoes.
Estimating evolutionary rates