Extreme thermal heterogeneity in structurally complex tropical rain forests

Abstract Most terrestrial species on Earth are ectothermic and track temperature at small spatial scales, from sun flecks to cool shaded spots. Current assessments of thermal heterogeneity in complex environments are predominately characterized by ambient temperature. This omission of solar radiation may lead to inaccurate conclusions regarding thermoregulation and distribution of species. We use thermal cameras to gather data on temperature heterogeneity in structurally complex rain forest environments. Using thermographic photographs, we capture the multidimensionality of climate created by vegetation by collecting over 76,000 temperature samples within approximately 1 m 2 quadrats. The method was tested against three standard methods that record air temperature to determine possible omissions in capturing thermal heterogeneity in four geographic locations—Colombia, Borneo, Madagascar, and Australia. Across all locations, there was greater thermal heterogeneity in surface temperature than captured from ambient temperature technologies. Spatial variability in surface temperature on 1 d was greater than temporal variability of ambient temperature across the entire month, with extreme deviation from ambient temperatures. Importantly, when compared to the lower bounds for optimal performance for five tropical Anolis species, this technology captured thermal regimes that support the thermoregulatory needs of these species, whereas ambient air temperature methods suggested that these species would be in thermal debt. Sampling surface temperature at high resolutions across space in combination with intensive sampling of ambient temperature and informed spatial modeling should improve our understanding of the distribution of ectothermic species living within thermally heterogeneous environments.