Thermal sensitivity of digestion in Sceloporus consobrinus, with comments on geographic variation

Description

Individual variation in energetics, environment, and genetics can influence population- level processes. However, it is often assumed that locally measured thermal and bioenergetic responses apply among broadly related species. Even closely related taxa may differ in the thermal sensitivity of performance, which in turn influences population persistence, population vital rates, and the ability to respond to environmental changes. The objectives of this project were to quantify the thermal sensitivity of digestive physiology in an Sceloporus lizards, to compare closely related, but geographically distinct, populations. Sceloporus lizards are a model organism, as they are known to exhibit thermally dependent physiologies and are geographically widespread. Digestive passage time, food consumption, fecal and urate production, metabolizable energy intake (MEI), and assimilated energy (AE) were compared for Sceloporus consobrinus in Arkansas and S. undulatus in South Carolina and New Jersey. Published data were acquired for NJ and SC lizards, while original data were collected for S. consobrinus. Comparisons of digestion among populations were made at 30°C, 33°C, or 36°C. Results suggest that digestive physiology differs among populations, with S. consobrinus being more efficient at warmer temperatures. In contrast, NJ and SC lizards had quicker passage times and lower fecal and urate production at 30ºC in comparison to AR. The results of the current study exemplify how closely related organisms can differ in thermal sensitivity of performance. Such data are important for understanding how individual-level processes can vary in response to climate, with implications for understanding variation in physiological traits across the range of Sceloporus lizards.

Steps to reproduce

To make direct comparisons of S. consobrinus in Arkansas and S. undulatus in SC and NJ, methods were replicated from Angilletta (2001b) where digestive parameters were measured for S. undulatus from NJ and SC. Following Angilletta (2001b), the influence of temperature on food consumption, passage time, fecal production, urate production, MEI, and AE was quantified by exposing lizards to one of three temperature treatments; 30°C (n = 14), 33°C (n = 12), or 36°C (n = 11). Temperatures were maintained using an environmental chamber ( 0.5ºC). During trials, lizards were maintained in plastic tanks (41.9 cm x 33 cm x 16.8 cm) lined with butcher paper, with a hide box, and provided water ad-libitum. Feeding trials were conducted using Fluker’s (Port Allen, LA) 2- and 3-week-old crickets (Acheta domestica) and began after lizards had been acclimatized for five days and had processed a meal, followed by a 3-day fasting period to clear the gut.

Institutions

Categories

Funding

Licence