Microhabitats reduce animal's exposure to climate extremes

Abstract

Extreme weather events, such as unusually hot or dry conditions, can cause death by exceeding physiological limits, and so cause loss of population. Survival will depend on whether or not susceptible organisms can find refuges that buffer extreme conditions. Microhabitats offer different microclimates to those found within the wider ecosystem, but do these microhabitats effectively buffer extreme climate events relative to the physiological requirements of the animals that frequent them? We collected temperature data from four common microhabitats (soil, tree holes, epiphytes, and vegetation) located from the ground to canopy in primary rainforests in the Philippines. Ambient temperatures were monitored from outside of each microhabitat and from the upper forest canopy, which represent our macrohabitat controls. We measured the critical thermal maxima (CTmax ) of frog and lizard species, which are thermally sensitive and inhabit our microhabitats. Microhabitats reduced mean temperature by 1-2 °C and reduced the duration of extreme temperature exposure by 14-31 times. Microhabitat temperatures were below the CTmax of inhabitant frogs and lizards, whereas macrohabitats consistently contained lethal temperatures. Microhabitat temperatures increased by 0.11-0.66 °C for every 1 °C increase in macrohabitat temperature, and this nonuniformity in temperature change influenced our forecasts of vulnerability for animal communities under climate change. Assuming uniform increases of 6 °C, microhabitats decreased the vulnerability of communities by up to 32-fold, whereas under nonuniform increases of 0.66 to 3.96 °C, microhabitats decreased the vulnerability of communities by up to 108-fold. Microhabitats have extraordinary potential to buffer climate and likely reduce mortality during extreme climate events. These results suggest that predicted changes in distribution due to mortality and habitat shifts that are derived from macroclimatic samples and that assume uniform changes in microclimates relative to macroclimates may be overly pessimistic. Nevertheless, even nonuniform temperature increases within buffered microhabitats would still threaten frogs and lizards.

Evaluating within‐population variability in behavior and demography for the adaptive potential of a dispersal‐limited species to climate change

“…Our results indicate resource availability will likely be restricted by future suboptimal conditions, so adaptive traits may be those that better secure resources such as suitable microhabitat. For many ectotherms, microhabitat can play an important role in buffering deleterious responses to climate change (Scheffers, Edwards, Diesmos, Williams, & Evans, 2014). However, the minimal variability in behavior in our population suggests physiological traits may become increasingly important.…”

Microrefuges and the occurrence of thermal specialists: implications for wildlife persistence amidst changing temperatures

“…As a result, the availability of microrefuges is often excluded from measurements that assess species' vulnerability to rapid environmental change [21]. Organisms can exploit microrefuges immediately to access favorable thermoclimatic profiles, foraging opportunities, nesting sites or shelter from extreme conditions [22][23][24]. In the case of temperature-sensitive species, individuals can exploit microhabitats that buffer otherwise stressful temperatures [23,25,26].…”

“…Organisms can exploit microrefuges immediately to access favorable thermoclimatic profiles, foraging opportunities, nesting sites or shelter from extreme conditions [22][23][24]. In the case of temperature-sensitive species, individuals can exploit microhabitats that buffer otherwise stressful temperatures [23,25,26]. Microclimate data, coupled with species occurrence information, can therefore help elucidate connections between species persistence and the availability of microrefuges.…”

Evidence that climate sets the lower elevation range limit in a high‐elevation endemic salamander

“…In large part, temperature alone is assumed to be a dominant control of the elevational limits of species and is thus used to model range shifts (Bernardo & Spotila, 2006; Forero‐Medina, Joppa, & Pimm, 2011; Forero‐Medina, Terborgh, Socolar, & Pimm, 2011; Thomas et al., 2004), although species‐level variation in rates of elevational change may be determined by other intrinsic and extrinsic variables (Chen et al., 2011). A range of models link climate and species’ occurrence data to forecast increased future extinction risk of high‐elevation species (Forero‐Medina, Joppa, et al., 2011; La Sorte & Jetz, 2010; Lawler et al., 2009) although some models predict species’ persistence where microrefugia exist in warming habitats (Dobrowski, 2011; Randin et al., 2009; Scheffers, Edwards, Diesmos, Williams, & Evans, 2013). The accuracy of these predictions is dependent on the relative importance of climate variables and species interactions for generating range limits (Pearson & Dawson, 2003).…”