Thermal Buffering of Microhabitats is a Critical Factor Mediating Warming Vulnerability of Frogs in the Philippine Biodiversity Hotspot

Abstract

Species may circumvent the impacts of climate warming if the habitats they use reduce ambient temperature. In this study, we identified which frog species from a tropical montane rain forest in the Philippines may be vulnerable to climate warming. To do so, we selected five anuran species that utilize four breeding habitats and identified the sensitivity and exposure of tadpoles and direct‐developer eggs to heat by measuring their critical thermal maximums (CTmax) and the habitat‐specific temperatures they experience. Our study species included two direct‐developer frogs—one species that lays its eggs on exposed leaves, and another that lays its eggs in ferns—and three species that produce aquatic free‐swimming tadpoles—two stream breeders, and one phytotelm (tree hole) breeder. We compared thermal tolerances derived from microclimates of breeding habitats with tolerances derived from macroclimate (i.e., non‐buffered air temperature taken from the rain forest canopy). We also examined whether differences in CTmax existed across life‐history stages (egg, metamorph/young‐of‐year, and adult) for the two direct‐developer frog species. Habitats buffered ambient temperature and expanded thermal tolerances of all frog species. We found that direct‐developers, however, are more vulnerable to increased temperatures than aquatic breeders—indicated by their high sensitivity to temperature, and exposure to high temperatures. Direct‐developer eggs were more sensitive to warming than both metamorph and adult life‐history stages. Thermally buffered microhabitats may represent the only protection against current and impending climate warming. Our data highlight the importance of considering sensitivity and exposure in unison when deciphering warming vulnerability of frogs.

Thermally buffered microhabitats recovery in tropical secondary forests following land abandonment

“…One iButton logger per plot was hung approximately 1 m above the ground to measure understorey ambient temperature (Scheffers, Brunner et al 2013). To identify the (near-)maximum potential ambient air temperature for our study plots, we hung a second iButton in the upper canopy cover of trees between ten and thirteen meters above the ground (Scheffers, Phillips et al 2013), as close as possible to directly above the understorey ambient logger depending on canopy accessibility.…”

Thermal buffering effect of alpine boulder field microhabitats in Australia: Implications for habitat management and conservation

“…Although the depths of some boulder field cavities may exceed 500 cm (personal observation), and no extremely deep temperatures were measured due to the difficulty of deploying sensors amid the complex rock cavity morphology, our data suggested a greater thermal buffering effect would occur in deep cavities. These buffering effects must be taken into consideration when evaluating the vulnerability of species to climate change (Williams et al, 2008) and overlooking these fine-scale effects may overestimate the vulnerability of species to climate change (Luoto and Heikkinen, 2008;Randin et al, 2009;Scheffers et al, 2013). For example, Brereton et al (1995) concluded that the bioclimatic range of B. parvus in Victoria will disappear with only a 1°C rise in mean air temperature.…”

Microhabitats reduce animal's exposure to climate extremes

“…Understanding acute climate exposure within microhabitats relative to the physiological sensitivities and limits of species that use them is critical in identifying species vulnerability to novel climates (Williams et al ., ; Duarte et al ., ; Scheffers et al ., ). A key research objective is understanding the role habitats will play in moderating the ecophysiological impacts of climate change on ectotherm communities (Huey & Tewksbury, ).…”