Intraspecific variation in climate‐relevant traits in a tropical rainforest lizard

Abstract

Aim The exceptionally rich biodiversity found in tropical rainforest is under threat from anthropogenic climate change. We recognize the threat, yet we have little knowledge of the capacity of tropical species to adjust their climate sensitivity in response to it. One indicator of a species’ capacity to adjust to different climates is the amount of intraspecific variation observed in its climate‐relevant traits; if a climate‐relevant trait varies, and this variation is correlated with local climates, it suggests the species can adjust the trait to different conditions through either phenotypic plasticity or evolutionary adaptation. Here, we test for intraspecific variation in climate‐relevant traits in a rainforest specialist to shed light on the capacity of such species to adjust to different climates. Location The Wet Tropics Bioregion, Australia. Methods We studied 12 populations of a lizard that is a tropical rainforest specialist, the rainforest sunskink (Lampropholis coggeri), testing for intraspecific variation in four traits that are potentially important in determining a species’ climate sensitivity. The measured traits were as follows: critical thermal minimum, critical thermal maximum, thermal optimum for sprinting, and desiccation rate. Results We found substantial variation both through time and across space in the measured traits, suggesting both strong plasticity and substantial geographic variation. Moreover, trait variation was correlated with local climate variables, suggesting variation reflects adjustment to local conditions. Main conclusions If physiological lability similar to that observed in rainforest sunskinks occurs in tropical rainforest species more generally, these taxa may not be as climatically specialized, and so not as vulnerable to climate change, as previously thought.

Thermoregulatory behaviour explains countergradient variation in the upper thermal limit of a rainforest skink

“…To our knowledge, this is the first published example of a common garden study testing for fixed heritable variation in CT max in lizards. Similar to the pattern seen in wild‐caught sunskinks (Llewelyn et al ), our common garden sunskinks whose parents came from the colder Pal population had higher CT max than those whose parents came from the hotter HR population (i.e. a negative correlation with thermal environment; Fig.…”

“…Our earlier study found the counterintuitive pattern that sunskinks from cooler environments tend to have higher upper thermal limits (CT max ; Llewelyn et al ). Here, we demonstrate that this pattern appears to be driven by behavioural shifts.…”

“…In this species, CT max shows considerable variation: CT max varies across populations, but also seasonally within populations by up to 4°C (Fig. ; Llewelyn et al ). The best environmental predictor of this variation is recent maximum environmental temperature, and surprisingly, CT max is negatively correlated with this variable (Fig.…”

“…The best environmental predictor of this variation is recent maximum environmental temperature, and surprisingly, CT max is negatively correlated with this variable (Fig. ; Llewelyn et al ): sunskinks from hotter environments have lower CT max . This pattern is counter to what we would expect if CT max was adjusted directly to local thermal conditions.…”

Peripheral Isolates as Sources of Adaptive Diversity under Climate Change

“…Because these peripheral isolates are naturally occurring and have often been in existence for at least several thousand years (many could be early Holocene relicts, sensu; Hampe and Jump, 2011), they provide a good snapshot of the adaptive capacity of a species (e.g., Llewelyn et al, 2016). If, based on size and connectivity, a species should be present in a patch but is not, then there might be a case that the environment in that location is too extreme, and beyond the limits of that species' capacity to adapt.…”