Rapid evolution of desiccation tolerance in field mesocosms. (A) Mean temperature and RH across the 10 replicate mesocosms are plotted over the duration of the experiment. (B) Mean (± s.e.m.) desiccation tolerance for females (closed symbols) and males (open symbols) at the four sampling time points in 2014. Tolerance increased for both females and males from July 25 to August 19 (F1,2357 = 339.91, p < 0.0001; F1,2358 = 9.63, p < 0.002, respectively). Over the period from September 11 to October 10, tolerance decreased in females (F1,2357 = 11.59, p < 0.001) and increased in males (F1,2357 = 41.44, p < 0.0001).