Correspondence between thermal preference and different fitness measures. In CB4856, thermal preference (the frequency of worms found at each temperature) correlates with LRS (left panel) but not r (right panel). The reverse is true for both CB4854 and CB4857, in which thermal preference correlates strongly with r. In PX174 thermal preference is correlated positively and about equally with both fitness measures, due to its broad, flat frequency distribution on a thermal gradient. Fitness values are least square means ± SEM. *p < 0.05.