title: Effect of body mass and melanism on heat balance in Liolaemus lizards of the goetschi clade.
abstract: The body temperature of ectotherms depends on the environmental temperatures and behavioral adjustments, but morphology may also have an effect. For example, in colder environments, animals tend to be larger and to show higher thermal inertia, as proposed by Bergmann's rule and the heat balance hypothesis (HBH). Additionally, dark coloration increases solar radiation absorption and should accelerate heat gain (thermal melanism hypothesis, TMH). We tested Bergmann's rule, the HBH and the TMH within the ITALIC! Liolaemus goetschilizard clade, which shows variability in body size and melanic coloration. We measured heating and cooling rates of live and euthanized animals, and tested how morphology and color affect these rates. Live organisms show less variable and faster heating rates compared with cooling rates, suggesting behavioral and/or physiological adjustments. Our results support Bergmann's rule and the HBH, as larger species show slower heating and cooling rates. However, we did not find a clear pattern to support the TMH. The influence of dorsal melanism on heating by radiation was masked by the body size effect in live animals, and results from euthanized individuals also showed no clear effects of melanism on heating rates. Comparison among three groups of live individuals with different degrees of melanism did not clarify the influence of melanism on heating rates. However, when euthanized animals from the same three groups were compared, we observed that darker euthanized animals actually heat faster than lighter ones, favoring the TMH. Although unresolved aspects remain, body size and coloration influenced heat exchange, suggesting complex thermoregulatory strategies in these lizards, probably regulated through physiology and behavior, which may allow these small lizards to inhabit harsh weather environments.
authors.affiliation: Laboratorio de Fotobiología, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA), CONICET-UNCOMA, Quintral 1250, San Carlos de Bariloche, Río Negro 8400, Argentina morenoal@comahue-conicet.gob.ar.
authors.forename: Débora Lina
authors.identifier: 0000-0002-8616-0544
authors.initials: DL
authors.lastname: Moreno Azócar
authors.affiliation: Laboratorio de Fotobiología, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA), CONICET-UNCOMA, Quintral 1250, San Carlos de Bariloche, Río Negro 8400, Argentina.
authors.forename: Marcelo Fabián
authors.initials: MF
authors.lastname: Bonino
authors.affiliation: Laboratorio de Fotobiología, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA), CONICET-UNCOMA, Quintral 1250, San Carlos de Bariloche, Río Negro 8400, Argentina.
authors.forename: María Gabriela
authors.initials: MG
authors.lastname: Perotti
authors.affiliation: Beloit College, 700 College Street, Science Center 338, Beloit, WI 53511, USA.
authors.forename: James A
authors.initials: JA
authors.lastname: Schulte
authors.affiliation: Facultad de Ciencias Naturales e I. M. Lillo (UNT), CONICET-Instituto de Herpetología (FML), San Miguel de Tucumán 4000, Argentina Miguel Lillo 205, San Miguel de Tucumán 4000, Argentina.
authors.forename: Cristian Simón
authors.initials: CS
authors.lastname: Abdala
authors.affiliation: Laboratorio de Fotobiología, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA), CONICET-UNCOMA, Quintral 1250, San Carlos de Bariloche, Río Negro 8400, Argentina.
authors.forename: Félix Benjamín
authors.initials: FB
authors.lastname: Cruz
mesh_terms: D000818:Animals; D001118:Argentina; D049628:Body Size; D001835:Body Weight; D005843:Geography; D006358:Hot Temperature; D016018:Least-Squares Analysis; D008116:Lizards / Q000502:physiology*; D008548:Melanosis / Q000503:physiopathology*; D008954:Models, Biological; D010802:Phylogeny; D013045:Species Specificity; D013997:Time Factors
keywords: Bergmann's rule; Cold climates; Heat balance hypothesis; Heating and cooling rates; Thermal inertia; Thermal melanism hypothesis