Acclimation scope of the critical thermal limits in Agalychnis spurrelli (Hylidae) and Gastrotheca pseustes (Hemiphractidae) and their implications under climate change scenarios

Abstract

We analyzed the acclimation scope in the critical thermal limits (CTmax and CTmin) in tadpoles of two Ecuadorian frog species which strongly differ in thermal habitat conditions and altitudinal distribution ranges: (1) Agalychnis spurrelli (Hylidae), Durango, Esmeraldas province, 200 m.a.s.l. and (2) Gastrotheca pseustes (Hemiphractidae), Ambato-Guaranda road, Bolivar province, 3467 m.a.s.l. The tadpoles were acclimated for a three days period and then their thermal tolerances were tested through a thermal bath which rise 0.25 °C/min. In both species, the CTmax and CTmin increased along with the acclimation temperature. Agalychnis spurrelli was tolerant to higher temperatures; however, Gastrotheca pseustes was a better cold tolerant. Gastrotheca pseustes had a wider tolerance range than Agalychnis spurrelli. The ARRmax was higher in Agalychnis spurrelli (0.14) than Gastrotheca pseustes (0.05). The maximum exposure temperature (Te) in microhabitat at present conditions was 26.19 °C for Agalychnis spurrelli and 20.52 °C for Gastrotheca pseustes. In RCP 2.6 and 8.5 scenarios, the Te in both species, tended to increase in the future. In spite of the fact that Agalychnis spurrelli was a heat tolerant and had a greatest acclimation scope than Gastrotheca pseustes in present and future scenarios, it was the most vulnerable. This result was different to the one expected because we assume that high altitude species are more vulnerable to climate change. The results suggest that the vulnerability of the frogs of different altitude have to be reevaluated in base to eco-physiological information.