Diel and seasonal variations in the thermal biology of San Cristobal Lava Lizards (Microlophus bivittatus). (February 2020)

• Record Type: Journal Article
• Authors: Rowe, John W.; Clark, David L.; Martin, Chelsea E.; Valle, Carlos
• Is Part Of: Journal of thermal biology. Volume 88(2019)
• Publication Date: 2020-02
• Subjects: Microlophus -- Galá -- Pagos -- Thermal biology; Thermobiology -- Periodicals; Temperature -- Periodicals; Biology -- Periodicals; Thermobiologie -- Périodiques; Thermobiology; Periodicals; 571.46
• DOI: 10.1016/j.jtherbio.2020.102518
• Languages: English
• ISSNs: 0306-4565

Abstract

Abstract: Thermal biology, and therefore energy acquisition and survival, of ectotherms can be affected by diel and seasonal patterns of environmental temperatures. Galápagos Lava Lizards live in seasonal environments that are characterized by a warm and wet period when reproductive activity is maximal, and cooler and drier period. With the use of radiotelemetric techniques to record lizard surface temperatures (Ts ), we studied the thermal ecology of the San Cristóbal Lava Lizard ( Microlophus bivittatus ) during both the warm and cool seasons over two years. During the diel activity period and when operative temperatures exceeded Tset-min, at least on rock faces without canopy, 52% or less of the Ts observations fell within the laboratory-determined Tset range (36–40 °C). Therefore, lizards may have avoided very warm midday temperatures in shaded microhabitats and the lag times in changes in Ts values occurred as operative temperatures rose rapidly during late morning warming phase. Lizards effectively thermoregulated during a year with moderate warm season temperatures and during a cool season that was unseasonably warm. In contrast, lizards less effectively thermoregulated during the warmest and coolest years of the study. We did not detect intersexual differences in thermoregulation although males may thermoregulate less effectively than do females during the cool season although we were unable to detect significant differences using our nonparametric statistical techniques. Highlights: Laboratory-determined physiological set-point for both sexes = 36–40 ∘C. Open rock faces allowed late morning heating and reduced late afternoon cooling rates . Near thermoconforming in shaded microhabitats occurred during warm afternoon hours . Less effective thermoregulation occurred under the warmest and coolest study periods . There were no intersexual differences in thermoregulation .