Applicant: The Australian National University

Species/Taxon: Mountain Dragon (Rankinia diemensis); Three-lined skink (Acritoscincus duperreyi); She-oak skink (Cyclodomorphus casuarinae); White's skink (Liopholis whitii); Bougainville's skink (Lerista bougainvillii); Mountain skink (Carinascincus orocryptus); Northern Snow skink (Carinascincus greeni); Southern Snow skink (Carinascincus microlepidotus); Spotted skink (Carinascincus ocellatus);Tasmanian Tree skink (Carinascincus pretiosus); Metallic skink (Carinascincus metallicus); Southern Grass skink (Pseudemoia entrecasteauxii); Blotched Blue-tongue lizard (Tiliqua nigrolutea); Southern Water Skink (Eulamprus tympanum)

Location: Work will primarily take place on private properties with owner permission, and none will be conducted within National Parks.

Title of research: Are viviparous squamates more vulnerable to climate change?

Aim of project: Anthropogenic global change has pushed life towards the cliff of a modern mass extinction, yet some organisms teeter closer toward the cliff’s edge than others. Ectotherms, which rely on their external environments to regulate body temperature, are particularly sensitive to global warming. There are two main mechanisms through which organisms can compensate for a rapidly rising temperatures: relocation to more favorable thermal environments, or thermal adjustment to new environmental conditions via plasticity or adaptation. However, any adjustment to higher body temperatures (Tb) will also bring these organisms closer to their upper thermal limits (critical thermal maximum), increasing the risk of overheating. Among ectotherms, such threats may be amplified in viviparous (live-bearing) species, which are often (though not universally) more cool-adapted than oviparous (egg-laying) close relatives. Extinction risks for viviparous organisms may increase due to embryonic development being compromised in utero due to higher maternal body temperatures. This project focuses on deciphering whether transitions to viviparity in squamates are associated with repeatable shifts in the optimum and pattern of thermal physiological evolution, and if these patterns increase certain groups vulnerability to climate change. In particular, the extent to which maternal thermal physiological traits and parity mode are intertwined remains to be seen. I propose to investigate the evolutionary signatures of parity mode on thermal physiological trait evolution across squamates and what that means for squamate vulnerability to climate change.

Justification: Temperature is well known to impact a myriad of life-history traits (e.g., growth, age at maturity, lifespan, reproductive investment) particularly in ectothermic organisms. These critical life-history traits can directly impact population dynamical patterns in nature. As such, understanding how the thermal physiological evolution has shaped the biodiversity and life-history patterns we see today is a key piece of the puzzle in determining how animals will respond to the changing and more variable climates Australia (and the globe) will experience in the future. These are significant questions of both national and international importance, and model lizard systems can greatly inform our understanding of how animals will respond to rapidly changing global conditions. Given these questions are physiological in nature, they require the use of living animals.

Maximum likely numbers of individuals involved: A maximum of 60 individuals per species (only 30 per species will be brought into the field lab for physiological measures.)

Activities undertaken and methods: When we capture a lizard we will measure cloacal temperature using a thermocouple (small temperature probe attached to a handheld temperature recorder). Estimates of thermoregulation are improved with sample size; up to 60 animals per species for Tb measures. The measurement of heat and cold tolerance (CTmax and CTmin) involve transiently stressing organisms so as to determine their physiological limits. By definition, measuring physiological limits involves stress as the procedure briefly pushes organisms outside of their comfort zone. However, these procedures are not lethal, and rather determine the functional limits of physiology, rather than the lethal limits of physiology. Thus, organisms are transiently stressed, but not to the point of death and, after the procedure, are rapidly returned to equilibrium. Fewer individuals are necessary for the these more stressful measures; up to 30 individuals/measure. The procedures have a long history in the physiological community and their utility for determining vulnerability to climate change is key. 

Fate of animals: Animals will be released at point of capture.