Fig. 3.

Hormonal and metabolic divergence among species across treatments. a Premetamorphic tadpoles of each spadefoot species were reared in high or low water level with exogenous CORT or metyrapone (Met, a CORT synthesis inhibitor) as shown. Species showing adaptive developmental acceleration in response to pond drying (P. cultripes and S. multiplicata) experienced steep increases in size-adjusted SMR when faced with reduced water level, which could be mimicked by treatment with exogenous CORT in high water and impaired by treatment with metyrapone in low water. In contrast, SMR in S. couchii was unresponsive to reduced water levels or even to exogenous CORT, hence showing a canalized high level of metabolism. b Whole-body CORT content was measured after 24 h in each treatment for each species. As expected, CORT content increased after low water treatment in P. cultripes and S. multiplicata, and exogenous hormone treatment increased CORT content in all species. Importantly, metyrapone treatment blocked the low water-induced increase in CORT content in P. cultripes and S. multiplicata, but metyrapone did not reduce the constitutive CORT content in S. couchii. Letters inside the bar graphs indicate significance groups within species based on post hoc significance tests. Sample sizes were as follows for the High, High+CORT, Low, Low+Met treatmentst: P. cultripes (10, 11, 10, 9), S. multiplicata (10, 10, 8, 10), and S. couchii (10, 10, 10, 10)