Competition with wall lizards does not explain the alpine confinement of Iberian rock lizards: an experimental approach

Interspecific competition can limit the distribution of species along altitudinal gradients. It has been suggested that Western European rock lizards (genus Iberolacerta) are restricted to mountains due to the expansion of wall lizards (Podarcis), but there is no experimental evidence to corroborate this hypothesis. This study examines if interference competition with Podarcis muralis is a plausible explanation for the alpine confinement of Iberian rock lizards Iberolacerta cyreni. In a first experiment, we used an enclosure with four types of microhabitats to investigate whether adult rock and/or wall lizards shifted microhabitat or refuge preferences in the presence of the other species, and to detect aggressive interactions between them. In a second experiment, we staged heterospecific encounters between naïve, laboratoryborn juveniles to identify behavioural differences and agonistic interactions. In the enclosure, neither rock nor wall lizards changed their microhabitat preferences in the presence of the other species. Nevertheless, rock lizards increased the diversity of microhabitats and nocturnal refuges used in the single species trials, which had twice the number of conspecifics. Aggressive interactions involved mainly large rock lizard males. Juveniles did not show any interspecific agonistic behaviour, but rock lizards spent more time basking and less time moving. Thus, we found no evidence of competition between both species in terms of habitat shifts or agonistic interactions, although intraspecific interactions seemed to explain the behaviour of adult rock lizards. We conclude that other factors are currently determining the alpine confinement of rock lizards.This paper is a contribution to the project CGL2007-02744/BOS, funded by the Spanish Ministry of Science and Innovation (MICINN).Peer reviewe

Altitude and Rock Cover Explain the Distribution and Abundance of a Mediterranean Alpine Lizard

West European Rock Lizards within the Iberolacerta group have a restricted distribution, with small, widely separated ranges in highland areas. The aim of this study was to identify possible habitat requirements (including habitat structure, type of vegetation, and refuge availability) and topographic factors (altitude and orientation) that may determine variations in the abundance of Iberolacerta cyreni on a 300-km2 mountain range and to discuss the implications of our results for the conservation of this endangered endemism. Both a stepwise regression and a best model selection approach showed that lizard abundance was positively correlated with only two predictors: altitude and cover of large rocks. Thus, the successful exploitation of alpine habitats by I. cyreni seemed to depend on the abundance of large rocks that may provide suitable basking substrates while minimizing predation risk. The positive association between altitude and lizard abundance predicts a fragmented distribution with isolated populations in the mountain peaks.This paper is a contribution to the project CGL2007-02744/BOS, funded by the Spanish Ministry of Education and Science. CM was funded by a CSIC-El Ventorrillo grant. We have complied with all applicable institutional Animal Care guidelines, and all required permissions were provided from the Dirección General del Medio Natural of the Madrid and Castilla y León región.Peer reviewe

Abundance, microhabitat selection and conservation of eyed lizards (Lacerta lepida): a radiotelemetric study

The utility of radiotelemetry as a tool for estimating the size and microhabitat requirements of a population of Lacerta lepida, the largest European lacertid, was investigated in central Spain. Population density estimates based on repeated marking and recapture (3.2 lizards ha 1) were much higher than those based on line transects (0.22 lizards ha 1). The probability of sighting lizards before they could retreat into a refuge was largely increased by our ability to radiolocate them. Rocks were selected as refuges 96% of the times, and the locations of radiotracked lizards were much closer to rocks than randomly expected. Rocks used as retreat sites were larger and had more crevices than those available at random, which suggests that refuge selection was primarily determined by the need to find shelter from predators. Rockrose patches, which were positively selected, might be used as refuge-connecting corridors that combine shelter with opportunities to forage and thermoregulate. Our results emphasize the need for using radiotelemetry to establish baseline information on abundance and to clarify the actuality, extent and pattern of the population declines experienced by species that may function as key links in their ecosystems, but the wariness of which poses a serious problem for monitoring their conservation status.This research was funded by DGESIC projects BOS2001-0533 and CGL2004-01151/BOS.Peer reviewe

Sexual dimorphism and interpopulation differences in lizard hind limb length: locomotor performance or chemical signalling?

Received 16 March 2011; revised 11 May 2011; accepted for publication 11 May 2011Intraspecific variation in morphology has often been related to fitness differences through its effects on performance. In lizards, variation in hind limb length can be shaped by natural selection for increased locomotor performance, sexual selection on the number or size of femoral pores involved in chemical signalling, or both. Here, we analyse the selective forces involved in sexual dimorphism and differences in hind limb length between two populations of Psammodromus algirus living at different elevation. Males were more robust and had longer hind limbs and limb segments than females, and low-elevation lizards had longer limbs than high-elevation lizards. However, differences in locomotor performance were small and non-significant, making natural selection for faster runs an unlikely explanation for the observed pattern. On the other hand, males had more femoral pores than females, and lizards had more pores at lower elevation, although the difference was significant only for males (which invest more in chemical signalling). In males, the number of pores, which remains constant along a lizard's life, was not correlated with hind limb length. However, femur length was positively correlated with mean pore size, allowing low-elevation males to have larger than expected pores, which could increase the effectiveness with which they spread their signals in a dry and warm habitat where chemicals become volatile rapidly. Also, saturation of the sexual coloration of the head was higher for low-elevation males, suggesting that sexual selection pressures may be more intense. Overall, our results indicate that sexual selection plays a significant role in shaping intraspecific variation in hind limb length.This paper is a contribution to projects CGL2007-60277/BOS and CGL2010-17928 funded by the Spanish Ministry of Education and Science.Peer reviewe

Living at the edge: lower success of eggs and hatchlings at lower elevation may shape range limits in an alpine lizard

Studies on range limits clarify the factors involved in the extent of species occurrence and shed light on the limits to adaptation. We studied the effects of elevational variation on the thermal dependence of fitness-related traits (incubation time, hatching rate, and survivorship, size, and condition of hatchlings) to assess the role of incubation requirements in distribution range limits of the alpine endemic Iberolacerta cyreni. We captured gravid females from two core (summit) and two marginal (low-elevation edge) populations, we incubated their eggs at three temperatures (22, 26, and 30 °C), and we monitored phenotypic effects. Viability of eggs and hatchlings decreased, independently of elevation, as incubation temperature increased. Hatching success and embryo survivorship were lower for clutches from low-elevation areas than for those from mountain summits, showing that lizards face difficulties thriving at the low-elevation edge of their range. Such difficulties were partly counterbalanced by faster postnatal growth at lower elevations, leading to increased adult size and higher fecundity. High incubation temperature had detrimental effects also at low-elevation areas, and no elevational variation in the thermal dependence of hatchling traits was detected. We suggest that temperature effects on egg development and the lack of selective pressures strong enough to foster local adaptation at marginal areas, combined with extended egg retention, may contribute to shape the range limits of these alpine oviparous reptiles

ESTIMATION OF THE PRIVATE AND SOCIAL RATE OF RETURN FROM EDUCATION IN LATVIA

IZGLĪTĪBAS PRIVĀTĀS UN SOCIĀLĀS ATDEVES NOVĒRTĒJUMS LATVIJĀ Anotācija Promocijas darba mērķis ir novērtēt izglītības ietekmi uz darba samaksu un darba produktivitāti indivīda un sabiedrības līmenī Latvijā, kā arī izstrādāt priekšlikumus izglītības nozīmes paaugstināšanai un atdeves novērtējuma lietošanai. Lai novērtētu izglītības privāto atdevi, tiek izmantota Mincera ienākumu funkcija, kā arī profesora E. de la Fuentes metodoloģija. Novērtējot sociālo atdevi, autore aprēķināja vīriešu un sieviešu (ar augstāko izglītību) cilvēkkapitālu laika posmā no 2000. līdz 2010. gadam un iegūtos rezultātus lietoja ražošanas funkcijā, aprēķinot izglītības ietekmi uz darba produktivitāti. Autore aprēķināja, ka recesijas periodā izglītības nozīme pieaug, kas vienlaikus norāda uz lielākām darba samaksas atšķirībām starp strādājošajiem ar dažādiem izglītības līmeņiem. Izglītības privātā atdeve augstākajā izglītībā pārsniedz vairāk nekā divas reizes atdevi no vidējās izglītības. Rezultāti liecina, ka sieviešu cilvēkkapitāla pieaugums pozitīvi ietekmē darba produktivitāti. Atslēgvārdi: cilvēkkapitāls, izglītība, izglītības privātā un sociālā atdeveESTIMATION OF THE PRIVATE AND SOCIAL RATE OF RETURN TO EDUCATION IN LATVIA Annotation The purpose of this Ph.D. thesis is to evaluate the impact of education on work salary and labour productivity at an individual and societal level in Latvia and to present suggestions for financing the education system. The Mincer earnings function and Professor Angel de la Fuente’s methodology are applied in estimating the private rate of return. The author estimates the human capital of women and men with higher education during 2000 – 2010 and applies the results in a regression model to estimate the impact of education on labour productivity and consequently on the social rate of return to education. The author estimated that during the period of recession the value of education has increased, and that indicates greater differences in work salary between employees with different education levels. The author estimates that the private rate of return from higher education is twice as high as the rate of return from secondary education in 2010. Results indicate that increase of female human capital has positive impact on the labour productivity. Key words: human capital, education, private and social rate of retur

Intraspecific variation in lizard heat tolerance alters estimates of climate impact

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: DP17010104

Heat tolerance is more variable than cold tolerance across species of Iberian lizards after controlling for intraspecific variation

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 (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 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 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 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

Lizard heat tolerance (Iberian Peninsula) / CTmax

Critical Thermal Maxima (CTmax) of 304 adult males belonging to 59 populations and 15 lizard species from the Iberian Peninsul

Data from: Heat tolerance is more variable than cold tolerance across species of Iberian lizards after controlling for intraspecific variation

[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 reviewe