Contents lists available at ScienceDirect Journal of Thermal Biology journal homepage: www.elsevier.com/locate/jtherbio Ornate tree lizards (Urosaurus ornatus) thermoregulate less accurately in habitats of high thermal quality Alannah H. Lymburner a,* , Gabriel Blouin-Demers a a Department of Biology, University of Ottawa, 30 Marie-Curie Private, Ottawa, Canada ARTICLE INFO Keywords: Body temperature Cost-benefit model Thermoregulation Ectotherm Thermal quality Habitat ABSTRACT Temperature plays a critical role for ectotherm performance and thus for fitness. Ectotherms, since unable to regulate their body temperature internally, use behavioural thermoregulation to maintain their body tempera- ture within a range that maximizes performance. According to the cost-benefit model of thermoregulation, investment into thermoregulation is dictated by the trade-off between the costs and benefits of thermo- regulating. The thermal quality of the environment is a major cost of thermoregulation because it directly affects the amount of time and energy that must be invested by an individual to achieve and maintain an optimal body temperature. Thus, in habitats of poor thermal quality, lizards should thermoregulate less. Using Urosaurus ornatus living at 10 sites each straddling two adjacent habitats (wash and upland), we tested the hypothesis that investment in thermoregulation is dependent on the thermal quality of the habitat. We found that the wash habitat had higher thermal quality indicated by a longer duration when optimal body temperatures could be reached. Lizards had more accurate body temperatures in the upland despite its poorer thermal quality. These results suggest that discrepancies in thermal quality between adjacent habitats affect investment in thermo- regulation by lizards, but in a direction opposite to the main prediction of the cost-benefit model of thermo- regulation. 1. Introduction Although environmental temperatures vary tremendously through space and time, most organisms regulate their body temperature within a narrow range. The ability to respond to environmental thermal gra- dients and maintain a T b within this narrow range is beneficial for the optimization of physiological processes (Huey and Bennett, 1987). For instance, a T b outside of this optimal range can have negative effects on locomotor performance, food acquisition (Zhang and Ji, 2004), and predator avoidance (Huey and Kingsolver, 1989). More ultimate mea- sures of fitness, such as reproductive output, are also linked to T b (Halliday et al., 2015). Consequently, T b has direct implications for the fitness of animals. Ectotherms are of particular interest when considering T b and its effects on performance due to their limited ability to regulate T b through metabolism (Huey and Kingsolver, 1989). Because ectotherms have low metabolic rates, they have limited physiological control over their T b and are dependent on other mechanisms of thermoregulation (Bennett, 1980; Huey and Kingsolver, 1989). As compared to en- dotherms, ectotherms use a more energetically affordable strategy of temperature regulation through behaviour. By altering their behaviour, ectotherms are able to control heat gain or loss through conduction, convection, evaporation, and radiation (Angilletta, 2009). Common behavioural strategies include basking, changing body posture (Huey, 1974), selecting particular microhabitats and activity periods (Adolph, 1990; Hertz and Huey, 1981; Stevenson et al., 1985). Using behavioural thermoregulation, ectotherms are able to maintain a T o and respond to environmental temperature changes (Glanville and Seebacher, 2006; Huey and Stevenson, 1979; Seebacher, 2005). Not all ectotherms thermoregulate to the same extent. Thermoregulatory strategies can range from thermoconformity, where the organism does not thermoregulate and T b matches the environ- mental temperatures (Ruibal, 1961), to active and nearly perfect ther- moregulation, where behaviour is used to adjust T b within a narrow range (Sartorius et al., 2002). Differences in the costs and benefits of thermoregulation are assumed to account for this variation (Huey and https://doi.org/10.1016/j.jtherbio.2019.102402 Received 6 August 2019; Received in revised form 22 August 2019; Accepted 23 August 2019 Abbreviations: T b , body temperature; T o , optimal body temperature; T set , preferred body temperature; T sk , skin temperature; d b , accuracy of body temperature; T e , operative environmental temperature; d e , thermal quality; SVL, snout-vent length; LMM, linear mixed model; d e -d b ,effectiveness of thermoregulation; E x , thermal exploitation index * Corresponding author. 30 Marie-Curie Private, Ottawa, Canada. E-mail addresses: alymb099@uottawa.ca (A.H. Lymburner), gblouin@uottawa.ca (G. Blouin-Demers). Journal of Thermal Biology 85 (2019) 102402 Available online 26 August 2019 0306-4565/ © 2019 Elsevier Ltd. All rights reserved. T