Mean (± SD) mass of killifish studied at each of three acclimation temperatures (19, 25 and 28°C).

Four species were studied, a pair from low altitude (A. splendopleure and A. ahli) and from high altitude (A. cameronense and A. exiguum), with two generations per species, an F0 generation captured in the wild and an F1 generation bred in captivity. Values are in mg, numbers in brackets are sample size. Data failed the Kolgorov-Smirnov test for normality, even after log transformation. Kruskal-Wallis one-way ANOVA by ranks found a significant difference (H = 46.552, d.f. = 23, P = 0.003) but Dunn's method for all pairwise multiple comparisons failed to identify any significant differences among groups (see Text S1 for details).