Italian wall lizard

Appearance

The snout–vent length of "P. siculus" is 150–250 mm on average. "P. siculus" is characterized by a green or brown back with a white or green belly. There is variation in length and color diversity due to the many subspecies and populations of "P. siculus." For example, some subspecies are melanic, meaning that parts of the back and belly have hints of blue. Such coloration is found on island populations of "P. siculus" rather than continental populations.Dipineto L, Raia P, Varriale L, et al.. "Bacteria and parasites in "Podarcis sicula" and "P. sicula klemmerii" ". "BMC Veterinary Research" 14 : 392. https://doi.org/10.1186/s12917-018-1708-5

Head size is a sexually dimorphic trait, with males having larger heads and stronger jaws than females. It is hypothesized that this size difference is due in part to prey consumption needs in males and male-male aggression.Taverne M,  Fabre A-C,  King-Gillies N, et al.  . "Diet variability among insular populations of "Podarcis" lizards reveals diverse strategies to face resource-limited environments". "Ecology and Evolution"  9 : 12408–12420. https://doi.org/10.1002/ece3.5626

Naming

"P. siculus" contains dozens of subspecies. Many different subspecies of "P. siculus" have been described, though some distinguished by very few morphological differences. Henle and Klaver described 52 subspecies of "P. siculus." Podnar et al described 6 groupings of "P. siculus" in the species’ native range. The first clade is the Sicula clade, which includes Southwestern Calabria, Sardinia, and Sicily. The Monesterace clade includes the Istrian coast. The Cantazaro clade includes central Calabria. The Tuscany clade spans across Western Italy. The Suzac clade includes islands in southern and central Dalmatia. The final clade is the Campestris-sicula clade, which spans Northern Italy and the Adriatic Islands inhabited by "P. siculus."

There have also been reports of hybridization between "P. siculus" and other species of the "Podarcis" genus, such as "P. tilguerta" and "P. raffonei."Populations of "P. siculus" in North America have been documented from Topeka, Kansas, Long Island, New York, Greenwich, Connecticut, Levittown, Pennsylvania, and the Greater Cincinnati area of Ohio, Indiana and Kentucky where P. siculus and P. muralis can both be found in very high concentrations and have become so well established that the Ohio Department of Natural Resources classifies now classifies them as a resident species rather than an invasive species because they are so successful and have been present for so long. Although illegal, it is not uncommon for people in the Greater Cincinnati Area to “trade” P. muralis lizards with people who live in areas with high population of P. siculus and then releasing significant numbers of the lizards in their own yards and rock walls.
The species seems to be extending its range from an initial colonization event in western Long Island, presumably by using railroad tracks as dispersal corridors. In 2020, a large number of "P. s. campestris" entered Great Britain as stowaways among shipments of grapes, before being intercepted.

"P. siculus" has also entered the Iberian Peninsula as an invasive species where it competes with the native "Podarcis virescens" species. Competition between the two lizard species has led to displacement of "P. virescens" lizards as they are outcompeted by "P. siculus" lizards.

Status

The Italian wall lizard is listed as being of least concern by the International Union for Conservation of Nature on the IUCN Red List. Its current population numbers are increasing.

Behavior

A 2005 study compared seasonal and diel behaviors of an introduced population of "P. siculus" to its Italian counterparts. The activity period of "P. siculus campestris" was reduced compared to "P. siculus" in Rome, where lizards are active year-round. Colder mean temperatures in the New York habitat of "P. siculus campestris" may explain why this population’s activity is limited to the months of April through October. "P. siculus campestris" was also active for fewer hours during the day compared to its Roman counterparts. The photoperiod of Long Island, New York, the home of "P. siculus campestris", is similar to that of Rome. This similarity strengthens the argument for temperature explaining the discrepancy in activity levels.Burke, Russell L.; Ner, Sylwia E.. "Seasonal and Diel Activity Patterns of Italian Wall Lizards, "Podarcis sicula campestris", in New York". "Northeastern Naturalist" 12 : 2005, 349–360. https://doi.org/10.1656/1092-6194012[0349:sadapo]2.0.co;2.

Habitat

"P. siculus" is a habitat generalist and thrives in many natural and human-modified environments. Habitats of "P. siculus" include forests, grasslands, shrublands, rocky areas, and farmland.Corti, Claudia; Biaggini, Marta; Berti, Roberto. "Different habitats, different pressures? Analysis of escape behaviour and ectoparasite load in "Podarcis sicula" populations in different agricultural habitats". "Amphibia-Reptilia" 30 : 453-461. https://doi.org/10.1163/156853809789647068 Web. It is able to live in such open habitats due to biological characteristics, such as high thermophily, which is the ability to thrive in high temperatures.A 2005 study compared seasonal and diel behaviors of an introduced population of "P. siculus" to its Italian counterparts. The activity period of "P. siculus campestris" was reduced compared to "P. siculus" in Rome, where lizards are active year-round. Colder mean temperatures in the New York habitat of "P. siculus campestris" may explain why this population’s activity is limited to the months of April through October. "P. siculus campestris" was also active for fewer hours during the day compared to its Roman counterparts. The photoperiod of Long Island, New York, the home of "P. siculus campestris", is similar to that of Rome. This similarity strengthens the argument for temperature explaining the discrepancy in activity levels.Burke, Russell L.; Ner, Sylwia E.. "Seasonal and Diel Activity Patterns of Italian Wall Lizards, "Podarcis sicula campestris", in New York". "Northeastern Naturalist" 12 : 2005, 349–360. https://doi.org/10.1656/1092-6194012[0349:sadapo]2.0.co;2.

Reproduction

"P. siculus" is oviparous. Females can lay 3 or 4 clutches of 4-7 eggs per year.Downes S, Bauwens D. "Does reproductive state affect a lizard's behavior toward predator chemical cues?". "Behavioral Ecology and Sociobiology" "52" : 444–450. https://doi.org/10.1007/s00265-002-0538-3 The number of eggs laid per clutch does vary by population. For example, populations on small islands of Croatia lay fewer eggs that hatch into larger offspring. The reproductive season of "P. siculus" begins in May and ends in July. Gravidity does not impose major physical burden upon females. Gravid females engage in more basking behavior than their non-gravid counterparts.

The activity of P450 in the brain of male "P. siculus" differs based on the reproductive stage of the individual. Importantly, P450 localizes to parts of the brain involved in reproductive and behavioral regulation. Thus, P450 is implied in the regulation of sexual behavior in "P. siculus."Santillo, Alessandra, et al.. "Aromatase Immunolocalization and Activity in the Lizard's Brain: Dynamic Changes during the Reproductive Cycle". "Comptes Rendus Biologies" 342 : 18–26. https://doi.org/10.1016/j.crvi.2019.01.002.

Food

"P. siculus" is a generalist predator. Its diet consists of a wide variety of invertebrates, mainly arthropods. "P. siculus" predates on small vertebrates as well.Bonacci, Teresa; Capula, Massimo; Brandmayr, Tullia Zetto; Brandmayr, Pietro; Aloise, Gaetano. "Testing the predatory behaviour of "Podarcis sicula" towards aposematic and non-aposematic preys". "Amphibia-Reptilia" 29: 449-453. https://doi.org/10.1163/156853808785111986 Web. Plant matter comprises a much greater percentage of the diet of "P. siculus" than other related lizards. There is also a disparity in diet diversity between the sexes, with males having a more diverse diet than females. Contrary to common ecological thought, there is little relationship between habitat area and diet diversity for "P. siculus". Different levels of taxonomic prey diversity does not seem to affect the diversity of diets in different "P. siculus" populations, but insular populations of "P. siculus" do consume a greater percentage of plant matter as a part of their diet."P. siculus" has a strong preference for the consumption of non-conspicuous prey. Conspicuous coloration is a strong deterrent of consumption of carabid beetles.Bonacci, Teresa. "Predator Feeding Choice on Conspicuous and Non-conspicuous Carabid Beetles: First Results". "ZooKeys" 100: 171–179. https://doi.org/10.3897/zookeys.100.1525. When consuming aposematic prey, "P. siculus" throws its head back and rubs its snout on the soil. Such behavior has been attributed to the unpalatability of aposematic prey. "P. siculus" is able to respond to chemical cues from some species of carabid beetles, evidence that the lizard has evolved to be able to detect the presence of dangerous chemicals in its prey.

Instances of extreme feeding behavior have been reported. One instance of cannibalism has been reported to have taken place between an adult male and a juvenile. The adult male captured the juvenile by biting down hard on his hips. An adult female has also been observed consuming a juvenile "Hemidactylus turcicus" in 2003, which is the first documented case of predation by "P. siculus" on a gecko. Additionally, an adult male has been observed feeding upon a dead adult "Suncus etruscus" in 2004. This is the first time "P. siculus" has been documented feeding upon the dead flesh of a small mammal.