Functional responses in a lizard along a 3.5-km altitudinal gradient

Physiological and metabolic performance are key mediators of the functional 
response of species to environmental change. Few environments offer such a multifaceted array of stressors as high-altitude habitats, which differ markedly in temperature, water availability, UV radiation and oxygen pressure compared to low-altitude 
habitats. Species that inhabit large altitudinal gradients are thus excellent models to 
study how organisms respond to environmental variation.
Location: Tenerife island, Canary Islands archipelago (Spain).
Taxon: Tenerife lizard (Gallotia galloti, Lacertidae).
Methods: We integrated data on age structure, thermal and hydric regulatory behaviour 
and four metabolic and stress-related biomarkers for an insular lizard that inhabits an 
extreme altitudinal range (sea level to 3700 m a.s.l.), to understand how an ectotherms' 
age, ecophysiology and metabolism can be affected by extreme environmental variation.
Results: We found marked differences in metabolic stress markers associated with 
altitude (particularly in the abundance of carbonyl metabolites and relative telomere 
length), but without a linear pattern along the altitudinal cline. Contrary to expectations, longer telomeres and lower carbonyl content were detected at the highest altitude, suggesting reduced stress in these populations. Evaporative water loss differed 
between populations but did not follow a linear altitudinal gradient. Lizard age structure or thermal physiological performance did not markedly change across different 
altitudes. Mixed signals in life-history and thermal ecology across populations and altitude suggest complex responses to variable conditions across altitude in this species.
Main Conclusions: Our integrative study of multiple functional traits demonstrated 
that adaptation to highly divergent environmental conditions in this lizard is potentially linked to an interplay between plasticity and local adaptation variably associated 
with different functional traits