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.