IHEM   20887
INSTITUTO DE HISTOLOGIA Y EMBRIOLOGIA DE MENDOZA DR. MARIO H. BURGOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Getting' High and Chillin': Cold Hardiness of Liolaemus Lizards Living Along an Elevation Gradient
Autor/es:
WARNER J.; E.A. SANABRIA; QUIROGA L.; ESPINOZA R.
Lugar:
Vancouver
Reunión:
Congreso; WORLD CONGRESS OF HERPETOLOGY VANCOUVER 2 0 1 2; 2012
Resumen:
Reptiles inhabiting cold-climates have evolved strategies to survive freezing temperatures. However, cold-hardiness adaptations have been studied in very few reptile species and no study has investigated cold-hardiness in a lineage that is distributed over an elevational gradient. We are studying the evolution of cold hardiness strategies of Liolaemus lizards living along an elevational gradient (1650?4070 m) in Argentina. Species were selected to represent multiple independent invasions of high-elevation living. We hypothesized that high-elevation (>3000 m) species will have either retained or evolved greater capacities to supercool and tolerate freezing in comparison to their low-elevation relatives. We tested the supercooling and freeze-tolerance capacities of six species of Liolaemus by cooling them below 0° C at an ecologically relevant rate. The extent that a lizard was able to supercool was determined as the temperature immediately before a dramatic rise in temperature is observed, as heat is liberated during the formation of ice. Freeze-tolerance capacities were determined by inoculating bodily ice formation near 0°C, then freezing the lizards to the lowest temperature recorded from their habitats. Estimates of the susceptibility of each species to freeze were determined by recording the temperature at which ice inoculation occurs. Lizards were then subjected to the minimum temperature for one of eight time treatments (15?180 min), then thawed and checked for survival. Percent ice composition was determined by calorimetry and related to survivorship. Data analyzed to date indicate that two of the high-elevation species and some individuals of the others can survive subzero body temperatures via supercooling and others are freeze tolerant. Analyses of data collected in summer 2012 will allow more thorough tests of our hypotheses.