Patterns of variations in dorsal colouration of the Italian wall lizard Podarcis siculus

ABSTRACT Research on animal colouration has grown exponentially in the last decade thanks to multidisciplinary approaches. Most studies are focused on trade-offs between communication and mimicry, which represent the two main constraints and drivers of the evolution of body colourations. Reptiles are excellent model species for investigating this field of study and lizards in particular show great variability of body colourations and their functions. We studied the lizard Podarcis siculus, analysing the variations of dorsal colour of three populations and obtained clear patterns of seasonal and ontogenetical variation of dorsal colour. According to baseline colour, males were greener and brighter than females, although no difference in saturation was recorded. According to seasonal variations, analyses showed that both sexes significantly vary in colour over the year: males reached higher peaks of hue and saturation later than females during spring, while females showed higher peaks of brightness and reached earlier similarly to hue and saturation. Ontogenetic variations were recorded only in males, which become greener, less bright and saturated with growing size. Therefore, our results suggest the occurrence of two opposing strategies in colour expression between sexes: males’ dorsal colouration plays a major role in communication, while females are more crypsis-oriented.

Invasive lizard has fewer parasites than native congener

Invasive species can carry parasites to introduced locations, which may be key to understand the success or failure of species establishment and the invasive potential of introduced species. We compared the prevalence and infection levels of haemogregarine blood parasites between two sympatric congeneric species in Lisbon, Portugal: the invasive Italian wall lizard (Podarcis siculus) and the native green Iberian wall lizard (Podarcis virescens). The two species had significant differences in their infection levels: while P. virescens had high prevalence of infection (69.0%), only one individual of P. siculus was infected (3.7%), and while P. virescens exhibited an average intensity of 1.36%, the infected P. siculus individual had an infection rate of only 0.04%. Genetic analyses of 18S rRNA identified two different haemogregarine haplotypes in P. virescens. Due to the low levels of infection, we were not able to amplify parasite DNA from the infected P. siculus individual, although it was morphologically similar to those found in P. virescens. Since other studies also reported low levels of parasites in P. siculus, we hypothesize that this general lack of parasites could be one of the factors contributing to its competitive advantage over native lizard species and introduction success.

Biological responses in pesticide exposed lizards (Podarcis siculus)

The release of contaminants as herbicides, fungicides and insecticides into the environment has been listed as one of the six major contributors to the global decline of reptiles. Although reptiles may face severe risk from contaminants due to their ecology and physiology, they are currently less studied than other vertebrate groups. In the present work, we investigated if and how different types of field treatment (conventional and organic) affected the health status of Italian wall lizard (Podarcis siculus) individuals in central Italy. We chose a multi-biomarker approach that evaluated the biological responses of lizards to the treatment by means of AChE activity in the nervous system, biotransformation enzymes activities and oxidative stress in the liver, micronuclei frequency measured in the erythrocytes, and rate of intestinal parasitic infection. Our findings showed evidence of effects of treatment in conventional areas and between sexes with significant oxidative stress due to hydroxyl radicals, that caused DNA damage. No difference of intestinal parasite infections was found among treatments. Podarcis siculus seems to be a good bioindicator in ecotoxicological studies and potentially in risk assessment of pesticides, although further analyses in laboratory and in the field are needed to achieve more accurate quantification of specific pesticide effects in relation to known exposure history and to understand if other mechanisms were involved in the toxicity and detoxification process of pesticides for this species.

Playing dead: lizards show tonic immobility without human handling

Tonic immobility, or the ability to play dead, is widespread among vertebrates. It is a last line of defence against a threat, and usually follows physical restraint. Here, I report two lizards exhibiting tonic immobility in the presence of humans, but remarkably, without any handling or physical contact. These two lizards belonged to an invasive population of the Italian Wall Lizard (Podarcis siculus), and both events took place in different years and situations, suggesting this behaviour may be more common than previously thought. There are rare documented cases of animals exhibiting this behaviour without handling; however, to my knowledge, this is the first description of a lizard displaying tonic immobility to humans, in the absence of handling. This is also the first incident of tonic immobility in the Italian Wall Lizard. I discuss these anecdotal events in the light of this invasive population inhabiting a highly urbanized location.

Occurrence of lizards in agricultural land and implications for conservation

Agriculture intensification is among one of the major threats affecting terrestrial reptiles worldwide. There is however a lack of information available on the ecology of these vertebrates in agricultural landscapes. Basic information like the pattern of occurrence in cultivated fields is key to assess the probability of an animal being affected by threats driven by agricultural managing. Focussing on the Italian wall lizard (Podarcis siculus), we performed a field study to assess in detail its distribution and abundance in two cultivations, vineyards and cereal fields. Lizard distribution and abundance significantly varied among land uses, regardless of the arthropod fauna composition and diversity (analysed in the same fields), and the management activities. In the cereal fields, lizards were present exclusively along the field margins while in the vineyards they also occurred in the inner portions of the cultivated areas, even if they were more abundant next to the borders. The widespread presence of lizards in the vineyards suggest that P. siculus can likely adapt to such cultivated areas. This partly lowers the effect of habitat loss due to vineyard planting but exposes animals to the risks related to management activities, including mechanical practices and chemical application. In contrast, the presence of sowed lands, as extremely simplified habitats, results primarily in a definitive loss of habitat for lizards that are unable to settle within them, while the exposure to threats driven by management is less direct than in vineyards.

First record of an Italian Wall Lizard (Podarcis siculus) in British Columbia, Canada

Italian Wall Lizard (Podarcis siculus) is known from scattered locations in the United States, including Orcas Island, Washington, where a population went unreported for about a decade, but was confirmed in 2017. On 19 June 2019, a single adult female P. siculus was caught in an industrial area along the northern arm of the Fraser River in Vancouver, British Columbia; this represents the first record of this species on the loose in Canada. No other P. siculus were sighted in the Vancouver area. We assume this Canadian P. siculus was a lone stow-away and had not deposited eggs. We could not determine how it entered the province.

Lizard colour plasticity tracks background seasonal changes

ABSTRACTEnvironmental heterogeneity on a spatial and temporal scale fosters an organism's capacity to plastically alter coloration. Predation risk might favour the evolution of phenotypic plasticity in colour patterns, as individuals who change colour throughout the year may be able to improve their fitness. Here we explored the change in dorsal pigmentation of the Italian wall lizard (Podarcis siculus campestris) at three time points (March, July, October) during a period of activity in a Mediterranean natural area in southern Italy. Following a preliminary investigation conducted in 2018, during 2019 we captured 135 lizards and took a picture of their ventral scales to check for possible recapture over the sessions. Lizard dorsal pictures were collected in the field with the support of a reference chart to quantitatively estimate chromatic variables (hue, saturation and value). At the same time, pictures of the environmental background were collected. Our findings suggest that lizards are capable of altering dorsal coloration during seasonal change. They vary from green at the onset of spring, to brownish in the middle of summer and to a greyish colour in October. This modification closely followed environmental background colour variation and enhanced lizard crypsis during each season.

Lizard colour plasticity tracks background seasonal changes

Environmental heterogeneity on spatial and temporal scale fosters organism’s capacity to plastically alter coloration. Predation risk might favour the evolution of phenotypic plasticity in colour patterns, as individuals, which change colour throughout the year, could be able to improve their fitness. Here we explored the change in dorsal pigmentation of the Italian wall lizard (Podarcis siculus campestris) along three time points (March, July and October) during the period of activity. Lizard dorsal pictures were collected on the field, with the support of a reference chart to quantitatively estimate chromatic variables (hue, saturation and value, HSV). At the same time, pictures of grassy coverings (the most representative portion of the environment subjected to normal seasonal change), were collected. Our findings show that lizards are capable of altering dorsal coloration during seasonal change. They vary from green, at the onset of spring, to brownish in the middle of summer, and greyish colour in October. This modification closely followed environmental background colour variation and enhanced lizard crypsis during each season.