Warmer isn't always better: Performance eurythermy in a cold-climate gecko

Area of Science:

• Zoology
• Ecology
• Physiology

Background:

• Ectotherm physiology and performance are highly temperature-dependent.
• Nocturnal ectotherms face challenges in achieving optimal body temperatures (Tb).
• Homonota darwinii, the world's southernmost gecko, inhabits cold climates, posing potential performance challenges.

Purpose of the Study:

• To investigate the thermal performance and latitudinal variation in sprint speed of Homonota darwinii.
• To test the hypothesis that southernmost populations exhibit greater thermal challenges and reduced performance.
• To understand the relationship between operative temperatures (Te) and sprint performance across different populations.

Main Methods:

• Sprint performance was measured at five ecologically relevant body temperatures (Tb).
• Four populations spanning the species' latitudinal range were studied.
• Annual operative temperatures (Te) were recorded in surface and refuge microhabitats.

Main Results:

• Sprint performance varied across the species' range but did not show a predicted decline with increasing latitude.
• Sprint performance was influenced by site-specific climatic variability, particularly elevation.
• Most populations displayed eurythermy, with optimal sprint performance across a broad range of body temperatures (Tb).

Conclusions:

• Homonota darwinii exhibits remarkable eurythermy, adapting to perform across a wide thermal spectrum.
• Latitudinal thermal challenges were not as predicted; instead, microclimatic variability plays a significant role.
• The findings contribute to understanding performance tradeoffs in nocturnal ectotherms inhabiting extreme environments.