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Heat tolerance is more variable than cold tolerance across species of Iberian lizards after controlling for intraspecific variation
Author(s) -
HerrandoPérez Salvador,
Monasterio Camila,
Beukema Wouter,
Gomes Verónica,
FerriYáñez Francisco,
Vieites David R.,
Buckley Lauren B.,
Araújo Miguel B.
Publication year - 2020
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1111/1365-2435.13507
Subject(s) - intraspecific competition , biology , population , ecology , maxima , demography , art , sociology , performance art , art history
The widespread observation that heat tolerance is less variable than cold tolerance (‘cold‐tolerance asymmetry’) leads to the prediction that species exposed to temperatures near their thermal maxima should have reduced evolutionary potential for adapting to climate warming. However, the prediction is largely supported by species‐level global studies based on single estimates of both physiological metrics per taxon. We ask whether cold‐tolerance asymmetry holds for Iberian lizards after accounting for intraspecific variation in critical thermal maxima (CT max ) and minima (CT min ). To do so, we quantified CT max and CT min for 58 populations of 15 Iberian lizard species (299 individuals). Then, we randomly selected one population from each study species (population sample = 15 CT max and CT min values), tested for differences between the variance of both thermal metrics across species, and repeated the test for thousands of population samples as if we had undertaken the same study thousands of times, each time sampling one different population per species (as implemented in global studies). The ratio of variances in CT max to CT min across species varied up to 16‐fold depending on the populations chosen. Variance ratios show how much CT max departs from the cross‐species mean compared to CT min , with a unitary ratio indicating equal variance of both thermal limits. Sampling one population per species was six times more likely to result in the observation of greater CT max variance (‘heat‐tolerance asymmetry’) than cold‐tolerance asymmetry. The probability of obtaining the data (given the null hypothesis of equal variance being true) was twice as likely for cases of cold‐tolerance asymmetry than for the opposite scenario. Range‐wide, population‐level studies that quantify heat and cold tolerance of individual species are urgently needed to ascertain the global prevalence of cold‐tolerance asymmetry. While broad latitudinal clines of cold tolerance have been strongly supported, heat tolerance might respond to smaller‐scale climatic and habitat factors hence go unnoticed in global studies. Studies investigating physiological responses to climate change should incorporate the extent to which thermal traits are characteristic of individuals, populations and/or species. A free Plain Language Summary can be found within the Supporting Information of this article.