CONICET | Buscador de Institutos y Recursos Humanos

The body temperature of ectotherms depends on the environmentaltemperatures and behavioral adjustments, but morphology may alsohave an effect. Forexample, in colder environments, animals tend to belarger and to show higher thermal inertia, as proposed by Bergmann?srule and the heat balance hypothesis (HBH). Additionally, darkcoloration increases solar radiation absorption and should accelerateheat gain (thermal melanism hypothesis, TMH). We testedBergmann?s rule, the HBH and the TMH within the Liolaemusgoetschi lizard clade, which shows variability in body size andmelanic coloration. We measured heating and cooling rates of liveand euthanized animals, and tested how morphology and color affectthese rates. Live organisms showless variable and faster heating ratescompared with cooling rates, suggesting behavioral and/orphysiological adjustments. Our results support Bergmann?s rule andthe HBH, as larger species show slower heating and cooling rates.However, we did not find a clear pattern to support the TMH. Theinfluence of dorsal melanism on heating by radiation was masked bythe body size effect in live animals, and results from euthanizedindividuals also showed no clear effects of melanism on heating rates.Comparison among three groups of live individuals with differentdegrees of melanism did not clarify the influence of melanism onheating rates.However, when euthanized animals fromthe same threegroups were compared, we observed that darker euthanized animalsactually heat faster than lighter ones, favoring the TMH. Althoughunresolved aspects remain, body size and coloration influenced heatexchange, suggesting complex thermoregulatory strategies in theselizards, probably regulated through physiology and behavior, whichmay allow these small lizards to inhabit harsh weather environments.

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