BUSCADOR RECOLECTA

Species are the unit of analysis in many global change and conservation biology studies; however, species are not uniform entities but are composed of different, sometimes locally adapted, populations
differing in plasticity. We examined how intraspecific variation in thermal niches and phenotypic plasticity will affect species distributions in a warming climate. We first developed a conceptual model linking plasticity and niche breadth, providing five alternative intraspecific scenarios that are consistent with existing literature. Secondly, we used ecological niche-modeling techniques to quantify the impact of each intraspecific scenario on the distribution of a virtual species across a geographically realistic setting. Finally, we performed an analogous modeling
exercise using real data on the climatic niches of different tree provenances. We show that when population differentiation is accounted for and dispersal is restricted, forecasts of species range
shifts under climate change are even more pessimistic than those using the conventional assumption of homogeneously high plasticity across a species’ range. Suitable population-level data are not available for most species so identifying general patterns of population differentiation could fill this gap. However, the literature review revealed contrasting patterns among species, urging greater levels of integration among empirical, modeling and theoretical research on intraspecific phenotypic variation., Comunidad de Madrid, Ministerio de Ciencia e Innovación, Red Iberoamericana de Ecología de la Conservación

Research addressing the effects of global warming on the distribution and persistence of species generally assumes that population variation in thermal tolerance is spatially constant or overridden by interspecific variation. Typically, this rationale is implicit in sourcing one critical thermal maximum (CTmax) population estimate per species to model spatiotemporal cross‐taxa variation in heat tolerance. Theory suggests that such an approach could result in biased or imprecise estimates and forecasts of impact from climate warming, but limited empirical evidence in support of those expectations exists.
We experimentally quantify the magnitude of intraspecific variation in CTmax among lizard populations, and the extent to which incorporating such variability can alter estimates of climate impact through a biophysical model. To do so, we measured CTmax from 59 populations of 15 Iberian lizard species (304 individuals).
The overall median CTmax across all individuals from all species was 42.8°C and ranged from 40.5 to 48.3°C, with species medians decreasing through xeric, climate‐generalist and mesic taxa. We found strong statistical support for intraspecific differentiation in CTmax by up to a median of 3°C among populations. We show that annual restricted activity (operative temperature > CTmax) over the Iberian distribution of our study species differs by a median of >80 hr per 25‐km2 grid cell based on different population‐level CTmax estimates. This discrepancy leads to predictions of spatial variation in annual restricted activity to change by more than 20 days for six of the study species.
Considering that during restriction periods, reptiles should be unable to feed and reproduce, current projections of climate‐change impacts on the fitness of ectotherm fauna could be under‐ or over‐estimated depending on which population is chosen to represent the physiological spectra of the species in question. Mapping heat tolerance over the full geographical ranges of single species is thus critical to address cross‐taxa patterns and drivers of heat tolerance in a biologically comprehensive way., Spanish Ministry of Economy and Competitiveness, Grant Number: CGL2011-26852; European Union, Grant Number: IC&DT1/SAESCTN/ALENT-07-0224-FEDER-001755; British Ecological Society, Grant Number: 4496-5470; Australian Research Council, Grant/Award Number: DP170101046

[Methods] Author contributions: Monasterio, Beukema and Gómes lead field (lizard sampling) and lab (estimation of thermal limits and measurement of body weights) work, and Monasterio and Araújo designed experiments. Herrando-Pérez conceived the idea of the two research manuscripts (Functional Ecology, Journal of Animal Ecology) and submitted the data to Dryad.

Funding: MBA partly funded through CGL2011-26852 project of the Spanish Ministry of Economy and Competitiveness. Field and experimental work funded by IC&DT 1/SAESCTN/ALENT-07-0224-FEDER-001755 project led by MBA.

Acknowledgements: We thank the Biological Station of “El Ventorrillo” for hosting the field team and for providing the thermal experimental facilities essential for this research. We also thank Tim Leerschool, Filipe Serrano and Matthijs Hollanders for their support in the field.

Collection permits: Samples, experiments and use of experimental animals supported for Portuguese populations by permits 360 to 362/2014/CAPT and 550 to 552/2014/CAPT (Instituto da Conservação da Natureza e das Florestas), and for Spanish populations by permits (autonomous communities in parenthesis hereafter) SGYB/EF/FJRH Re-9H/13 & SGYB/AF/DBP Re-79y131/14 (Andalucía), 2014-500201724/2014/02343 & INAGA/5000201/24/2013/04434 (Aragón), DGMEN/SEN/avp_13_025_aut & DGMEN/SEN/avp_14_020_aut (Castilla La Mancha), P/CYL/101/2013 & EP/CYL/106/2014 (Castilla y León), CN0023/14/ACA1587(14) (Extremadura), 2566/RX131316//clave031/2013 & 2241/RX123724//clave018/2014 (Galicia), and 10/033298.9/13 & 10/013907.9/14 (Madrid).

[Usage Notes] Content of dataset: Critical Thermal Maxima (CTmax) and Critical Thermal Minima (CTmax) and body weights of 304 male individuals belonging to 59 populations and 15 species of Iberian lizards (Dryad doi: 10.5061/dryad.1553pc3). Body weight, CTmax and CTmin available for all populations except the Moncayo/Soria/Spain population of Podarcis muralis for which CTmin was not measured.

Dataset set used in two research manuscripts: Intraspecific variation in lizard heat tolerance alters estimates of climate impact / Journal of Animal Ecology (doi: 10.1111/1365-2656.12914) and Heat tolerance is more variable than cold tolerance across species of Iberian lizards after controlling for intraspecific variation / Functional Ecology (in press).

Versions of dataset: the first version of the dataset contained CTmax data alone (Journal of Animal Ecology), species names, population codes, locality names (with region, country, lat/long), the second version of the dataset (Functional Ecology) contains the latter information along with CTmin and body-weight data while the locality names and lat/long have been refined., 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 if cold-tolerance asymmetry holds for Iberian lizards after accounting for intraspecific variation in critical thermal maxima (CTmax) and minima (CTmin). To do so, we quantified CTmax and CTmin for 58 populations of 15 Iberian lizard species (299 individuals). Then, we randomly selected one population from each study species (population sample = 15 CTmax and CTmin values), tested for variance homoscedasticity 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. The ratio of variances in CTmax to CTmin across species varied up to 16-fold depending on the populations chosen. Variance ratios show how much CTmax departs from the cross-species mean compared to CTmin, 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 CTmax variance (‘heat-tolerance asymmetry’) than cold-tolerance asymmetry. The null hypothesis of equal variance 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., British Ecological Society, Award: 4496-5470. European Union, Award: IC&DT 1/SAESCTN/ALENT-07-0224-FEDER-001755. Spanish Ministry of Economy and Competitiveness, Award: CGL2011-26852., Peer reviewed