Habitat management alters thermal opportunity

Abstract

Ectotherms engage in behavioral thermoregulation to optimize body temperatures, however, thermoregulatory effort varies across species, over time, and among habitats. Classic cost‐benefit models of ectothermic thermoregulation postulate that ectotherms should increase thermoregulatory effort when the benefits of thermoregulatory behavior outweigh the costs (Huey and Slatkin, 1976). However, alteration of habitat via land management may lead to unforeseen shifts in microclimate that change associated costs and benefits. In light of anthropogenic impacts on natural habitats, thermoregulatory effort should be examined in cases where land management results in environmental temperatures that deviate from the preferred temperature range of a given species. We examined how habitat management alters microclimates and influences activity time, thermoregulatory behavior, and thermal physiology in a lizard (Sceloporus woodi) whose range has been significantly reduced due to habitat loss. We compared populations from two ecologically distinct habitats: longleaf pine and sand pine scrub, which have very different management histories. Daily surveys were conducted in each habitat type while environmental temperatures were recorded simultaneously with biophysical models. Thermal performance curves differed between populations such that physiological performance was optimized in each environment. Longleaf pine habitat had greater thermal opportunity because cooler microclimates were available on arboreal perches. In longleaf pine habitat, lizards were able to stay active longer and thermoregulate more effectively. Regardless of habitat, thermoregulatory effort of S. woodi increased when thermal quality of habitat was low. However, when unfavorably high temperatures were experienced, the thermoregulatory effort increased significantly. Our results demonstrate that ectotherms can afford to imprecisely thermoregulate when habitat thermal quality is poor due to cooler environmental temperatures. However under unfavorably hot environmental temperatures, lizards must precisely regulate body temperature in spite of any costs. These results further demonstrate that habitat management has major implications on species‐specific thermal opportunity, thermoregulatory behavior, and thermal physiology, such that shifts in thermoregulatory behavior may lead to higher energetic costs, enhanced predation risk, and constrained activity times. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.fec13123/suppinfo is available for this article.

Longleaf pine proximity effects on air temperatures and hardwood top-kill from prescribed fire

“…Hardwoods, particularly mesic oaks, develop cavities that are utilized by bats and snakes (Howze et al 2019). Small clumps of hardwoods may have value as thermal or fire-free refuges for organisms of limited mobility (Neel and McBrayer 2018;Roe et al 2019). The ecological value of individual or small groups of hardwoods in a longleaf pine matrix, as opposed to the deleterious effect of mass hardwood recruitment from fire exclusion, implies the need for information on selective control of hardwoods using prescribed fire.…”

Mite load predicts the quality of sexual color and locomotor performance in a sexually dichromatic lizard

“…We did not determine that body temperature was related to badge color brightness or black border brightness in the present study. Likely, this is because the temperature gradients provided in this study encompassed scrub lizard operative temperatures, within which they were permitted to freely thermoregulate (Neel & McBrayer, ). However, lizards with increased mite loads did have higher body temperatures in the laboratory (Figure ).…”

“…All lizards were housed individually on sand and provided light (on a 12L:12D photoperiod from 0700 to 1900) from commercially available 75‐watt incandescent and ultraviolet lamps. This lighting system provided both light and a temperature gradient of 32–28°C to allow adequate basking and thermoregulation according to the preferred temperature range of scrub lizards (Cowles & Bogart, ; Neel & McBrayer, ). Water and food were provided ad libitum.…”

Acclimatization in the physiological performance of an introduced ectotherm

“…The thermal performance curve of each individual lizard was estimated by fitting a set of left-skewed parabolic equations to sprint data using the program TableCurve 2D (Systat Software, Inc.) (Angilletta, 2006;Logan et al, 2014;Neel and McBrayer, 2018). Equations were chosen based on the typical left-skewed shape of ectotherm thermal performance curves, which are thought to be structured by the thermodynamics of enzyme function (Somero, 1978).…”