No abstract

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.

Body temperatures, heat exchange rates, behavioral thermoregulation, and movement behavior (as an index of foraging mode) were studied in two widely distributed medium—sized lacertid lizards (Acanthodasctylus erythrurus and Psammodromus algirus). P. algirus mainly inhabits broad—leaved forests, whereas A. erythrurus prefers open, sandy areas with sparsely distributed vegetation. These habitat preferences parallel differences between the areas in which both genera presumably originated: Eurosaharian xeric steppes with high operative temperatures (Te) for Acanthodacylus, and Mediterranean open Forest with lower Te for Psammodromus. Field observations showed that percentage of time spent basking and basking rate (number of basks per minute) were negatively related to Te, although average bask duration was not. Percentage of time spent moving, moving rate (number of moves per minute), and the average duration of individual moves were inversely related to Te and were higher in P. algirus. The percentage of total locomotion time that was spent moving in the shade was also higher in P. algirus. Behavioral thermoregulation strategies differed in laboratory thermogradient, where P. algirus basked more often and for shorter periods and selected warmer patches than did A. erythrurus. Selected body temperatures (Tb) in a laboratory thermogradient were significantly higher in A. erythrurus than in P. algirus. Shade Seeking Tb was higher in A. erythrurus, but Resume Basking Tb did not differ significantly between the two species. Heating and cooling rates also differed in the two species: A. erythrurus warmed more slowly and cooled faster than did P. algirus. Our data support the existence of a complex syndrome that combines aspects of the behavior, physiology, and ecology of both species. The thermal consequences of inhabiting a certain type of habitat can be counterbalanced by behavioral and physiological means that, in turn, affect movement and, hence, foraigng behavior. Thus, the more active species (P. algirus) heated faster, cooled more slowly, and basked more often but for shorter periods and at warmer patches than thee less active species (A. Erythrurus).

One of the primary assumptions of the immunocompetence handicap hypothesis is that testosterone has an immunosuppressive effect, but conflicting results have been reported in a variety of bird species concerning the effect of testosterone on the humoral and the T cell-mediated components of the immune system. The T cell-mediated component of the immune system is particularly important during the breeding season, because the likelihood of injury during sexual competition is high and T cell-mediated immunity is essential for healing wounds and resisting infection. In this study we examined the effect of experimentally increased levels of testosterone during breeding season on T cell-mediated immunity in male lizards of two Mediterranean lacertid species, Psammodromus algirus and Acanthodactylus erythrurus. The hormonal treatment significantly increased testosterone of the experimental individuals. T cell-mediated responses to phytohemagglutinin stimulation were significantly suppressed in testosterone-treated males of both species. Furthermore, there was a significant negative relationship between individual variability in T cell-mediated responsiveness and plasma testosterone concentration. The present study is the first to demonstrate testosterone-induced suppression of T cell-mediated immunity in lizards.

Some Mediterranean wetlands are found between the areas with the highest prevalence of lead pellet exposure for waterfowl in the world. To assess the situation in Spain, availability of pellets in sediments and rates of ingestion by waterfowl were determined in four important wetlands: Albufera de València, El Fondo, Tablas de Daimiel, and Doñana (Guadalquivir Marshes). Lead pellet density in sediment was maximum in the Albufera, with 2.8 million pellets/ha. In Tablas de Daimiel, where hunting was banned in 1965, about 1.0 million pellets/ha were found. Percentages of shot waterfowl with ingested pellets were maximum in the wetlands on the Mediterranean coast (El Fondo and Albufera de València): 87.5% of common pochard (Aythya ferina) and approximately 33% of mallard (Anas platyrhynchos) and shoveler (Anas clypeata) contained ingested pellets. It was found that mallards with > 5 µg/g dry weight of lead in the liver had 8.5% lower body condition and 7.7% less body weight than birds with lower lead concentrations. Moreover, lead poisoning was diagnosed as the cause of death in 16 out of 75 birds, mainly greylag geese (Anser anser), found dead in some of these zones.

Many animals exhibit dramatic responses when subjected to a stressor. A classic marker of the stress response is an increase in plasma glucocorticoids, but this constitutes only one step in the cascade from experience of a stressor to wider organismal changes, including behavior. The behavioral sensitivity to glucocorticoids would determine the consequences of the stress-related alteration of behavior for the organism. In this study we explored, under laboratory conditions, the prenatal and postnatal effects of corticosterone on activity and thermoregulation of juveniles of the common lizard, Lacerta vivipara. Activity was measured as the time spent moving and the time spent scratching the wall in an empty terrarium. Thermoregulatory behavior was measured as the time spent motionless under a light bulb. Activity and thermoregulation of juveniles of the common lizard showed a different sensitivity to prenatal and postnatal corticosterone treatment, modulated by juvenile sex and maternal condition. Prenatal corticosterone manipulation influenced the time spent moving in both sexes. By contrast, only juvenile females increased the time spent scratching the walls of the terrarium when corticosterone was delivered both at the prenatal and postnatal stage. Prenatal hormone manipulation increased the time spent basking by juveniles issued from large females. These results suggest that, in addition to influencing a variety of behavioral and morphological traits, corticosterone may also play an important role in the regulation of activity and thermoregulation of juvenile lizards, modulated by individual sex and maternal condition.

Current and past parasite transmission may depend on the overlap of host distributions, potentially affecting parasite specificity and co-evolutionary processes. Nonetheless, parasite diversification may take place in sympatry when parasites are transmitted by vectors with low mobility. Here, we test the co-speciation hypothesis between lizard final hosts of the Family Lacertidae, and blood parasites of the genus Schellackia, which are potentially transmitted by haematophagous mites. The effects of current distributional overlap of host species on parasite specificity are also investigated. We sampled 27 localities on the Iberian Peninsula and three in northern Africa, and collected blood samples from 981 individual lizards of seven genera and 18 species. The overall prevalence of infection by parasites of the genus Schellackia was ∼35%. We detected 16 Schellackia haplotypes of the 18S rRNA gene, revealing that the genus Schellackia is more diverse than previously thought. Phylogenetic analyses showed that Schellackia haplotypes grouped into two main monophyletic clades, the first including those detected in host species endemic to the Mediterranean region and the second those detected in host genera Acanthodactylus, Zootoca and Takydromus. All but one of the Schellackia haplotypes exhibited a high degree of host specificity at the generic level and 78.5% of them exclusively infected single host species. Some host species within the genera Podarcis (six species) and Iberolacerta (two species) were infected by three non-specific haplotypes of Schellackia, suggesting that host switching might have positively influenced past diversification of the genus. However, the results supported the idea that current host switching is rare because there existed a significant positive correlation between the number of exclusive parasite haplotypes and the number of host species with current sympatric distribution. This result, together with significant support for host-parasite molecular co-speciation, suggests that parasites of the genus Schellackia co-evolved with their lizard hosts.

We studied the effect of hatching date on breeding performance (chick growth and mortality) and phenology (creching and fledging ages) of the chinstrap penguin during three years. The year affected every variable considered, probably due to pack‐ice persistence and food availability differences between years. Hatching date had slight or no effect on mortality and early growth, but was negatively correlated with creching age, which, in turn, was positively related to final size. The decision to leave the chicks unguarded does not seem to be based on the condition of the chicks, but on that of adults. Fledging age was negatively correlated with hatching date, and this effect was more marked in the year with poor growth performance. Given the short time available for breeding in Antarctica, there must be conflicting pressures between investing in feeding chicks and advancing the period of premoult resource storage, this explaining the strong relationship between hatching dates and subsequent phenological events (creching and fledging). In this kind of study, it may be important to remove the effect of inter‐year variation before assessing the possible effects of other variables.