Body size often varies with elevation, yet the proximate mechanisms underlying such patterns remain poorly understood. In the Mediterranean lizard Psammodromus algirus, body size increases stepwise with elevation, remaining stable between 300 and 1,200 m but increasing linearly from 1,700 to 2,500 m a.s.l. To identify the proximate mechanisms driving this pattern, we evaluated five non-mutually exclusive hypotheses: variation in (1) hatchling size, (2) juvenile growth rate, (3) time to sexual maturity, (4) post-maturational growth rate, and (5) longevity. We combined data from hatchlings, juveniles, and adults collected along the elevational gradient to test each mechanism. Elevational variation in lizard body size was not explained by variation in hatchling size, age at maturity, post-maturational growth, or longevity. Instead, juvenile growth rate increased significantly with elevation and was positively correlated with adult body size. This pattern was associated with greater prey abundance at high elevations, suggesting that faster juvenile growth in food-rich environments allows lizards to reach larger sizes despite shorter activity seasons. Our findings highlight that geographic variation in body size may reflect environmental constraints, underscoring the importance of identifying proximate mechanisms to understand phenotypic patterns in nature.

OBJECTIVE:Borrelia lusitaniae is a lizard-associated spirochaete which shows highly genetically structured populations in western Europe. Our objective was to assess whether selective forces acting on the Ixodes tick vector or the reservoir lizard, Psammodromus algirus, shaped its population structure. METHODS:We collected ticks feeding on P. algirus in the Iberian Peninsula and north Africa, and genetically characterized B. lusitaniae, the infected ticks, and the vertebrate host. RESULTS:The goeBURST analysis on seven MLST B. lusitaniae genes identified two main clusters: one from central Europe and other from north Africa and Portugal (south of Tagus river), with some connections between the north Tagus populations in central Spain and north African ones. The Ixodes sp. nuclear gene trospA did not entirely correspond with the B. lusitaniae population structure. The P. algirus's phylogeny based on the ND4 mitochondrial gene also did not show lineage distinctions between north and south Tagus. CONCLUSION:Both the clustering of B. lusitaniae lineages from this region together with those of south Portugal and north Africa, and the presence of ticks belonging to different trospA clades, suggests Central Spain, a contact area between lineages of P. algirus, as pivotal in the phylogeography of the host, its ticks and Borrelia.

Haematophagous ectoparasites draw resources from their hosts, reducing host body condition and altering haematology and immune physiology. The tick Ixodes ricinus is a hard tick whose immature stages can infest the lizard host Psammodromus algirus along its geographic distribution. However, few studies have examined the associations between tick infestation and lizard immune physiology and susceptibility to other infections. In this study, we analysed the geographic variation in tick ectoparasitism in P. algirus across 17 sites in the Iberian Peninsula and North-western Africa. We also examined the relationship between tick pressure, immune physiology, and haemoglobin concentration in these lizards. In addition, we tested whether P. algirus hosts infested by ticks were more often infected with blood parasites. All ticks found on P. algirus from the Iberian Peninsula belonged to the I. ricinus species, while the genera Hyalomma and Haemaphysalis were found only on P. algirus from Morocco. Tick prevalence and infestation intensity varied widely among geographic locations. All lizards from a single sampling site in central Spain were infested and harboured the highest tick loads, but no lizards from southern Spain were infested. Intermediate values of infestation were found in Portugal and Morocco. Infested adults harboured more ticks than infested juveniles. The presence and number of ticks were not correlated with the lizards' leucocyte counts nor with the heterophil-tolymphocyte ratio, but infested males had a lower H/L ratio than infested females. No significant relationship was found between tick infestation and the presence of blood parasites. We also tested the inter-individual variation in haemoglobin concentration of lizards in a single site, and it was not explained by tick load. Our results show that tick ectoparasitism in P. algirus hosts drastically varies across geography, but it did not correlate with the lizards' immune histology, haematic physiology, or status of infection by blood parasites.

Sexual size dimorphism (SSD), typically the result of different optimal body sizes for males and females, shows an enormous inter- and intraspecific variation. Lizards have become a model in the study of SSD, as they show either monomorphism, male- or female-biased SSD. Variations in the strength of intrasexual selection (assumed to favor larger body size in males) and fecundity selection (assumed to favor larger body size in females) are usually considered the main reasons for variation in SSD. Here, we take advantage of a 2,200 m elevational gradient for studying the elevational variation in SSD in the Mediterranean lizard Psammodromus algirus. Previous studies on this species suggest that the strength of sexual selection decreases with ascending elevation, while the strength of fecundity selection on females increases with ascending altitude. Accordingly, we predicted that SSD bias to males should increase at low elevations, while female-biased SSD should increase at high altitudes. We found that both males and females were larger with ascending elevation, but the magnitude of variation in body size with altitude differed between sexes. Females were slightly larger than males (1.1%), although SSD bias toward females increased with elevation. SSD was male-biased only in one locality, at the lowest elevation. Nevertheless, elevational differences in SSD resulted from a concomitant sexual variation in age structure, as females were older than males in every locality except at the lowest elevation, where males were older than females. Since this species shows post-maturational growth, sexual differences in age structure could explain the elevational pattern in SSD.

Haematophagous ectoparasites draw resources from their hosts, reducing host body condition and altering haematology and immune physiology. The tick Ixodes ricinus is a hard tick whose immature stages can infest the lizard host Psammodromus algirus along its geographic distribution. However, few studies have examined the associations between tick infestation and lizard immune physiology and susceptibility to other infections. In this study, we analysed the geographic variation in tick ectoparasitism in P. algirus across 17 sites in the Iberian Peninsula and North-western Africa. We also examined the relationship between tick pressure, immune physiology, and haemoglobin concentration in these lizards. In addition, we tested whether P. algirus hosts infested by ticks were more often infected with blood parasites. All ticks found on P. algirus from the Iberian Peninsula belonged to the I. ricinus species, while the genera Hyalomma and Haemaphysalis were found only on P. algirus from Morocco. Tick prevalence and infestation intensity varied widely among geographic locations. All lizards from a single sampling site in central Spain were infested and harboured the highest tick loads, but no lizards from southern Spain were infested. Intermediate values of infestation were found in Portugal and Morocco. Infested adults harboured more ticks than infested juveniles. The presence and number of ticks were not correlated with the lizards’ leucocyte counts nor with the heterophil-to-lymphocyte ratio, but infested males had a lower H/L ratio than infested females. No significant relationship was found between tick infestation and the presence of blood parasites. We also tested the inter-individual variation in haemoglobin concentration of lizards in a single site, and it was not explained by tick load. Our results show that tick ectoparasitism in P. algirus hosts drastically varies across geography, but it did not correlate with the lizards’ immune histology, haematic physiology, or status of infection by blood parasites.

Sexual size dimorphism is a hot topic in evolutionary ecology as it is influenced by a plethora of selective pressures. In this study, we investigated this issue in a painted frog Discoglossus pictus auritus population from south Tunisia, while controlling for age effects. Our results showed no significant sexual dimorphism in body size, classifying the painted frog among the few anuran species where the females are not larger than the males. However, foot webbing length showed a significant male-biased dimorphism, a pattern that may reflect selective pressure favoring swimming in males. Enlarged webbings could possibly improve a male’s mating success through greater aptitudes to win competition against rivals for egg fertilization. Therefore, our findings suggest a male-biased dimorphism in a locomotion-related character in an anuran species, a trait possibly under sexual selection.

Genetic differentiation between populations inhabiting ecologically different habitats might appear because of limited dispersal and gene flow, which may lead to patterns of phenotypic divergence and local adaptation. In this study, we use dispersal, genotypic (24 microsatellite loci) and phenotypic (body size and clutch size) data to analyse patterns of genetic structuring and phenotypic divergence in a blue tit (Cyanistes caeruleus) population inhabiting a continuous and heterogeneous woodland along a valley. The two slopes of the valley differ in their forest formations and environmental conditions. Findings showed that most blue tits reproduced within their natal slope. Accordingly, microsatellite analyses revealed that populations of blue tits established in the two slopes show subtle genetic differentiation. The two genetic populations diverged in clutch size, exceeding the level of differentiation expected based on genetic drift, hence suggesting divergent selection (or other processes promoting divergence) on this life-history trait. Our findings reveal that restricted dispersal and spatial heterogeneity may lead to genetic differentiation among bird populations at a surprisingly small scale. In this respect, it is worth highlighting that such differentiation occurs for an organism with high dispersal capacity and within a continuous woodland. Moreover, we show that small-scale ecological differences, together with limited gene flow, can result in selection favouring different phenotypes even within the same continuum population.

Parasites impact host fitness and constitute an important selective pressure on the host's life history. According to parasite-mediated sexual selection, ornaments are presumed to honestly indicate immune capacity or resistance against parasites, and the chooser sex (typically females) obtains an advantage by selecting more ornamented, thus more immunocompetent mates. Therefore, signalers mounting an immune response must allocate resources from the sexual signal to the immune system, hence reducing the expression of the ornament and becoming less attractive to the choosing sex. Here, we test this idea in the lizard Psammodromus algirus. We inoculated a subsample of males with lipopolysaccharide (LPS) of the cell wall of Escherichia coli, while others served as sham controls. The inoculation of LPS decreased the proportion of ergosterol (pro-vitamin D2) in femoral secretions, and chemosensory tests showed that the scent of LPS-inoculated males was less attractive to females than the scent of control males. Given that ergosterol is a precursor of vitamin D, which has physiological functions as an immune modulator, immunocompromised males likely needed to divert vitamin D to the immune system, reducing the allocation of ergosterol to secretions. In this way, females could detect "sick" males, preferring the apparently healthy males. Overall, our study shows that mounting an immune response is costly in terms of reduced attractiveness. Moreover, we disentangle the underlying mechanism, which involves an honest signal based on vitamin D allocation.

Several animals present ornamental colouration which acts as signals in sexual or other social contexts by indicating some trait of the bearer. This colouration is often present only in one sex and may be produced by a varied combination of structural elements and several pigments. Given that colours may be produced in different ways, the traits the colouration is indicating, and the costs or trade?offs associated, may differ according to the colour and the species studied. Here, I study a dark ventral colouration present in males of the gecko Quedenfeldtia trachyblepharus, a high-altitude, semi-colonial lizard endemic to the High Atlas in North Africa. I tested for the correlation between the extension of the dark colouration and several morphological traits (body size, head size and limb length) in the gecko, as well as parasitism by mites and age. No relationship was found between dark colouration and parasitism, age and limb length, but the extension of the dark colouration was positively correlated with head size controlled for body size. Given that head size is usually a good indicator of fighting capacity, and this gecko shows a strong social structure, the findings suggest that the dark colouration is used in agonistic encounters among males, allowing for evaluation of the fighting capacity of the rivals.

The roles of temperature and humidity in shaping diurnal retreat site occupation and short-term movements in amphibians in desert environments have scarcely been studied. In this work, we investigated retreats and movements in the painted frog (Discoglossus pictus auritus) that inhabits oases in arid southern Tunisia, by using a composite temperature-humidity index (THI). Our results show non-random occupation of retreat sites with respect to prevailing temperature-humidity conditions. When leaving retreat sites with THI values above or below their preferred levels, painted frogs tended to move to sites with THI levels more similar to their preferred conditions. We also found that large individuals tended to occupy retreat sites offering similar THI levels, while small individuals moved between sites with very different THI levels, a pattern that could be driven by age-dependent experience. However, there was no significant relationship between the distance moved by painted frogs and the magnitude of the change in the THI between occupied sites. In summary, our findings evidence the role of temperature-humidity conditions in shaping the patterns of diurnal retreat site use in an arid zone amphibian. They also underline the usefulness of composite temperature-humidity indices when assessing amphibian-habitat relationships.

Mediterranean woodland environments are characterised by high spatial and temporal heterogeneity, which means the inhabiting species face a wide variety of selective pressures. Species may respond differently to habitat heterogeneity and so distinct eco-evolutionary scenarios may be responsible for the inter-habitat variability in reproductive strategies observed in certain species. The inter-forest variability of some reproductive traits in passerines has been examined by comparing forest patches or separated fragments. However, there is still little information regarding how such highly mobile animals adjust their breeding performance across continuous and heterogeneous woodlands. Here we studied the reproductive performance of a population of Blue Tits (Cyanistes caeruleus) in an area of continuous Mediterranean woodland that included two mountain slopes and four different types of forest, ranging from deciduous oak forests to perennial non-oak forests. We studied the habitat heterogeneity and inter-forest phenotypic variation in terms of reproductive performance and adult and nestling biometry, besides also exploring the effects of ectoparasites on Blue Tit reproduction. Eggs were laid earliest in deciduous Pyrenean Oak (Quercus pyrenaica) forests, while clutch size and the number of fledglings were highest in the humid Pyrenean Oak forest, which had the greatest tree coverage and most humid climate, and lowest in the coniferous Scots Pine (Pinus sylvestris) forest. There were no inter-forest differences in hatching (percentage of nests with at least one egg hatched) and fledging (percentage of nests in which at least one nestling fledged) success. Similarly, there were no inter-forest differences in adult and nestling biometry, but adults that raised more fledglings had a lower body mass, while males whose females laid larger clutches had smaller tarsi. Most ectoparasites did not affect Blue Tit reproduction, although Culicoides had a negative impact on nestling body mass. These results suggest that Blue Tits can adjust their reproductive effort to the forest where they breed even across a very small spatial scale. Different eco-evolutionary scenarios, such as phenotypic plasticity or genetic structuring and local adaptation, might explain the phenotypic differentiation in the reproductive strategies observed over small areas in woodlands.

Filarioid nematodes (commonly known as filarial worms) are known to impact human and domestic animal health, but studies examining their ecological relevance and impacts on wildlife are still underrepresented. In the case of birds, microfilariae are typically found at low prevalence, but they may negatively affect some fitness-related traits. Here, we study the prevalence and associations of microfilariae in a wild population of blue tits (Cyanistes caeruleus) inhabiting a woodland comprising different forestry formations. In addition, we characterize the filarioid lineages through the cytochrome c oxidase subunit I (COI) gene sequence. We found a moderate prevalence of microfilariae in the blue tit population (9.4%) and that the presence of such parasites was negatively associated with host body mass. Neither forest type nor host sex influenced microfilariae presence. Phylogenetic analyses revealed the presence of five filarioid lineages clustered in the Onchocercidae family-four out of five lineages clustered in the Splendidofilaria clade, while the remaining lineage could not be clearly assigned to a genus. In addition, this is the first study examining the filarioid lineages infecting the blue tit. Our results suggest that hosts in poorer body condition, in terms of lower body mass, are more susceptible to be parasitized by filarioid nematodes and call for further genetic studies of these parasites.

Marking methods that do not affect survival are crucial to study anuran demography. Toe-clipping is among the most frequent marking methods in anurans. Nonetheless, the potential effect of toe-clipping on locomotion-and consequently on survival-is controversial. We studied a free-ranging population of Iberian green frogs (Pelophylax perezi) to test whether toe-clipping reduces jumping distance. Also, we compared return rates of frogs identified by toe-clipping and tagging with passive integrated transponders (PITs) after 1 year. We found no effect of toe-clipping on jumping distance, which minimizes the likelihood of toe-clipping diminishing return rates. Accordingly, we detected similar return rates in frogs marked by toe-clipping and PIT-tagging. Both techniques proved similarly efficient, although toe-clipping is cheaper and faster than PIT-tagging.

Human activities have caused massive losses of natural populations across the globe. Like many groups, amphibians have experienced substantial declines worldwide, driven by environmental changes such as habitat conversion, pollution, and disease emergence. Each of these drivers is often found in close association with the presence of roads. Here we report a novel consequence of roads affecting an amphibian native to much of North America, the wood frog (Rana sylvatica). Across 38 populations distributed from southern to central New England, we found that adult wood frogs living adjacent to roads had higher incidence and severity of oedema (indicated by obvious bloating caused by subcutaneous fluid accumulation) during the breeding season than frogs living away from the influence of roads. This effect was best explained by increased conductivity of breeding ponds, probably caused by runoff pollution from road salt used for de-icing. Oedema severity was negatively correlated with locomotor performance in more northerly populations. Interestingly, northern populations experience more intense winters, which tends to result in more de-icing salt runoff and increased energetic demands associated with overwintering cryoprotection needs. Thus, this emerging consequence of roads appears to impose potential fitness costs associated with locomotion, and these effects might be most impactful on populations living in regions where de-icing is most intense. Together, our findings reveal a novel set of impacts of roads and runoff pollution on wood frog physiology and performance, which seem likely to contribute to population decline. Given the global prevalence of roads and increasing salinisation of freshwater habitats, oedema and related impacts could be widespread consequences faced by amphibian populations across much of the planet's temperate zones.

Wild birds are hosts of Culicoides from as early on as the nesting stage when constrained to their nests. However, the environmental factors which determine the abundance and composition of Culicoides species within each bird nest are still understudied. We sampled Culicoides from Eurasian blue tit (Cyanistes caeruleus) nests found in 2 types of forests located in southern Spain. Firstly, we monitored the abundance of Culicoides species in bird nests from a dry Pyrenean oak deciduous forest and a humid mixed forest comprising Pyrenean and Holm oaks throughout 2 consecutive years. During the 3rd year, we performed a cross-fostering experiment between synchronous nests to differentiate the role of rearing environment conditions from that of the genetically determined or maternally transmitted cues released by nestlings from each forest. We found 147 female Culicoides from 5 different species in the birds' nests. The abundance of Culicoides was higher in the dry forest than in the humid forest. Culicoides abundance, species richness and prevalence were greater when the nestlings were hatched later in the season. The same pattern was observed in the cross-fostering experiment, but we did not find evidence that nestling's features determined by the forest of origin had any effect on the Culicoides collected. These results support the notion that habitat type has a strong influence on the Culicoides affecting birds in their nests, while some life history traits of birds, such as the timing of reproduction, also influence Culicoides abundance and species composition.

Several ectoparasites parasitise nestlings decreasing their body condition, growth and survival. To minimise any loss of fitness due to ectoparasites, birds have developed a wide variety of defence mechanisms, potentially including hatching asynchrony. According to the Tasty Chick Hypothesis (TCH), the cost of parasitism would be reduced if ectoparasites tend to eat on less immunocompetent nestlings, typically the last-hatched chick in asynchronously hatched broods, as they are in poor body condition. Two predictions of the TCH are that immune capacity is lower in smaller nestlings than in larger ones and that parasites should provoke a more negative effect on smaller nestlings. Here, we test these predictions in a population of Blue Tits (Cyanistes caeruleus) whose broods are parasitised by Hen Fleas (Ceratophyllus gallinae) and Blowflies (Protocalliphora azurea). We recorded the presence of both ectoparasites and analysed the immunocompetence (number of leucocytes per 10,000 erythrocytes and cutaneous immune response to phytohaemagglutinin) and body condition of smaller and larger nestlings within individual broods. The leucocyte count was higher in smaller nestlings than in larger ones, whereas the cutaneous immune response did not differ between smaller and larger nestlings. Smaller nestlings, but not larger nestlings, had lower body mass when fleas were present. Blowflies, by contrast, had no detectable negative effect on nestlings. Overall, our findings provide partial support to the TCH. Lower immune capacity in smaller nestlings than in larger ones was not supported, but Hen Fleas seemed to negatively impact on smaller nestlings more than on larger ones.

Bergmann's and Allen's rules were defined to describe macroecological patterns across latitudinal gradients. Bergmann observed a positive association between body size and latitude for endothermic species while Allen described shorter appendages as latitude increases. Almost two centuries later, there is still ongoing discussion about these patterns. Temperature, the common variable in these two rules, varies predictably across both latitude and elevation. Although these rules have been assessed extensively in mammals across latitude, particularly in regions with strong seasonality, studies on tropical montane mammals are scarce. We here test for these patterns and assess the variation of several other locomotory, diet-associated, body condition, and thermoregulatory traits across elevation in the Mountain Treeshrew (Tupaia montana) on tropical mountains in Borneo. Based on morphological measurements from both the field and scientific collections, we found a complex pattern: Bergmann's rule was not supported in our tropical mountain system, since skull length, body size, and weight decreased from the lowest elevations (<1000 m) to middle elevations (2000-2500 m), and then increased from middle elevations to highest elevations. Allen's rule was supported for relative tail length, which decreased with elevation, but not for ear and hindfoot length, with the former remaining constant and the latter increasing with elevation. This evidence together with changes in presumed diet-related traits (rostrum length, zygomatic breadth and upper tooth row length) along elevation suggest that selective pressures other than temperature, are playing a more important role shaping the morphological variation across the distribution of the Mountain Treeshrew. Diet, food acquisition, predation pressure, and/or intra- and inter-specific competition, are some of the potential factors driving the phenotypic variation of this study system. The lack of variation in body condition might suggest local adaptation of this species across its elevational range, perhaps due to generalist foraging strategies. Finally, a highly significant temporal effect was detected in several traits but not in others, representing the first phenotypic variation temporal trends described on treeshrews.

Oxidative status has been proposed as an important ecological and evolutionary force given that pro-oxidant metabolites damage molecules, cells and tissues, with fitness consequences for organisms. Consequently, organisms usually face a trade-off between regulating their oxidative status and other physiological traits. However, environmental stressors and the availability of dietary-derived antioxidants vary according to local conditions and, thus, organisms inhabiting different habitats face different oxidative pressures. Still, there is little information on how different environmental conditions influence the oxidative status of animals inhabiting terrestrial environments. In this work, we examined the variation in oxidative status in the blue tit (Cyanistes caeruleus), a bird species with hatching asynchrony. Specifically, we examined the oxidative status of the largest and the smallest nestlings in the brood, inhabiting four forests differing in food availability and ectoparasite prevalence. We measured lipid peroxidation (malondialdehyde; MDA) as a marker of oxidative damage, total antioxidant capacity (Trolox-equivalent antioxidant capacity; TEAC) and antioxidant enzymatic activity (catalase, glutathione S-transferase, glutathione peroxidase) in blood samples. The glutathione peroxidase (GPX) activity differed among the forests, being the highest in the pine forest and the lowest in a mixed oak (Quercus) forest in the most humid area. Lipid peroxidation was higher in larger nestlings, suggesting higher oxidative damage with an increasing growth rate. Neither brood size, laying date, nor ectoparasites were related to the oxidative status of nestlings. These results suggest that nest rearing conditions might shape the oxidative status of birds, having consequences for habitat-dependent variation in regulation of oxidative status.