Vertical and diel niches modulate thermal selection by rainforest frogs

Area of Science:

• Ecology
• Evolutionary Biology
• Herpetology

Background:

• Thermoregulatory behavior is crucial for an organism's physiological condition and can vary across climate gradients.
• Two key patterns are coadaptation (higher preferred temperatures in warmer locations) and countergradient variation (lower preferred temperatures in warmer locations).

Purpose of the Study:

• To investigate thermoregulatory behavior in rainforest amphibians across a vertical climate gradient (forest floor to canopy) and between diurnal and nocturnal activity periods.
• To determine if amphibians exhibit coadaptation or countergradient thermal selection in this understudied microclimate gradient.

Main Methods:

• Conducted 216 ground-to-canopy surveys, capturing 2534 amphibians from 37 species.
• Performed 282 thermal selection assays, pairing them with microclimate measurements and mechanistic model predictions.

Main Results:

• Amphibians exhibited countergradient thermal selection, with canopy-dwelling species selecting warmer temperatures than forest-floor species.
• Species consistently selected temperatures warmer than their exposed microclimates, particularly nocturnal arboreal species.

Conclusions:

• Multidimensional climate gradients (vertical and diel) are critical for understanding thermoregulatory behavior and evolutionary adaptations in species.
• Rainforest amphibians appear to significantly underutilize the warmer end of their thermal niches.