Strength of selection
Given non-zero heritability, stronger natural selection—the differential survival or reproduction of mosquitoes with different trait values—would lead to faster adaptive responses, despite causing high initial mortality (Lynch and Lande 1993, Hartl and Clark 1997). Temperature-imposed selection on mosquitoes, which can be approximated from temperature-dependent survival rates (Box 1, \(\gamma\); Falconer and Mackay 1996), is likely to be strong. Upper thermal limits for adult and larval survival are as low as 32-38°C (reviewed in Mordecai et al. 2019), which many mosquito populations—particularly those in the tropics—already experience and will increasingly face in a warming climate (Deutsch et al. 2008). Further, steep declines in survival between thermal optima and critical limits have been observed across mosquito species (Focks et al. 1993, Alto and Juliano 2001, Kamimura et al. 2002, Delatte et al. 2009, Muturi et al. 2011, Mordecai et al. 2019). This high selection pressure may facilitate mosquito adaptation, provided that heritable variation in trait thermal tolerance exists.