Gas Production
Total gas production over the 6 week-period was approximately 10% greater in adapted communities compared to both control and pre-adapted communities (Figure 2A, one-way ANOVA, F(2,32)=12.9,P value < .0001, Tukey HSD: Pre-adapted – Adapted, mean = 353.7, mean difference 95% CI [-529.8, -177.5], p<0.001, Control - Adapted, mean = 245.9, mean difference 95% CI [-422.0, -69.7], P = 0.005). The effect of community treatment on gas production varied over time (Figure 2B, LMM; effect of time × adaptation treatment on gas production: χ2(10) = 66.03, P value < 0.001), with gas production being significantly higher in the adapted communities from 3 weeks onwards (see Supplemental Table 1 for contrasts). This delay in the increase in gas production argues against the possibility that gas production increased in the adapted communities because of physiological or nutritional changes resulting from the 1% addition of the pre-adapted communities. Instead, the delay suggests community members introduced from the pre-adapted communities that contributed to higher gas production increased in frequency from rare.