Podarcis sicula (Italian wall lizard)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Natural Food Sources
- Latitude/Altitude Ranges
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Impact Summary
- Environmental Impact
- Threatened Species
- Risk and Impact Factors
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Podarcis sicula (Rafinesque-Schmaltz, 1810)
Preferred Common Name
- Italian wall lizard
Local Common Names
- Germany: ruineneidechse
Summary of InvasivenessTop of page
The Italian wall lizard, P. sicula, is a reptile species that has been introduced worldwide. Its native range comprises the Italian Peninsula, Sicily and the north Adriatic coast, while its introduced range extends from the Mediterranean Islands, Iberian Peninsula, Greece and Turkey to the UK, North Africa and the USA. This lizard is very eclectic in its habitat use, being found both in natural areas, agricultural environments and urban areas. It tends to use trees and man-made structures as refuges, which enhances its accidental transportation. These ecological traits together with its behavioural characteristics have led to the successful introduction and spread of P. sicula to new environments where it can negatively impact native lizards through competition, displacement and hybridization. As well as affecting several native and endemic species it is also reported as affecting the critically endangered Aeolian wall lizard (P. raffonei) and endangered Lilford's wall lizard (Podarcis lilfordi).
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Chordata
- Subphylum: Vertebrata
- Class: Reptilia
- Order: Sauria
- Family: Lacertidae
- Genus: Podarcis
- Species: Podarcis sicula
Notes on Taxonomy and NomenclatureTop of page
Henle and Klaver (1986) stated a total of 52 described subspecies of Podarcis sicula, 47 endemic to islands. However, it is important to note that most of them are based on very small morphological differences or small samples. Podnar et al. (2005) found some incongruences on the described subspecies’ mitochondrial genes, which shows that care should be taken when dealing with subspecies and that further studies are needed. Currently, of the multiple subspecies described, three are widely accepted: P. s. campestris (northern half of Corsica and Italy), P. s. cetti (southern Corsica and Sardinia) and P. s. sicula (Italy and Sicily).
Surrounding the genus, there is some debate as to whether Podarcis is feminine or masculine (Böhme, 1998; Arnold, 2000; Böhme and Köhler, 2005; Montori and Llorente, 2005). Here we follow the original nomenclature, in order to prevent possible confusions and because there is no statement by the International Commission on Zoological Nomenclature pronouncing that is wrong.
In its native range, P. sicula is distributed into six well-supported groups (clades; Podnar et al., 2005). Three southern sub-groups exist including the Sicula clade - southwestern Calabria, Sicily and Sardinia; the Monesterace clade – one locality on the Istrian coast (southeastern Calabria) and the Cantazaro clade – central Calabria. Three ‘northern’ sub-groups include the Tuscany clade – northern areas of western Italy (from Rome to Tuscany itself); the Suzac clade – islands in southern and central Dalmatia and the Campestris-sicula clade – northern Italy and most of Adriatic range. The pattern found by Podnar et al. (2005) is interpreted as a combination of a series of natural events, such as glacial refuges and postglacial area expansion, and multiple introductions by man.
Hybridization with other species from the Podarcis genus has also been documented. Capula and his colleagues reported the hybridization between P. sicula and P. tiliguerta (Capula, 2002), P. raffonei (Capula et al., 2002) and P. wagleriana (Capula, 1993).
DescriptionTop of page
The Italian wall lizard (P. sicula) can measure up to 9 cm in length, although it is usually found to be a bit smaller. Its morphology is highly variable, but it normally has a fairly long head and robust body, a whitish, greyish or greenish tinge belly (almost always without dark spots), and a green, yellowish, olive or light brown dorse. It exhibits sexual dimorphism; females are smaller and have a smaller head than males, and also lack the enlarged base of the tail and femoral pores (Vogrin, 2005). Regional variations of the morphology can be found in Arnold and Ovenden (2002).
DistributionTop of page
The native range of P. sicula comprises the Italian Peninsula, Sicily and the North Adriatic Coast. From there it was introduced to some Mediterranean islands; other European places, such as the Iberian Peninsula, Greece, the UK, Switzerland, France, Turkey; North Africa and the USA.
In islands and islets surrounding the Italian Peninsula and northwest Adriatic Coast it has been difficult to disentangle the allochonous status of the populations, both because of ancient presence of human activities (Blondel et al., 2010) and because some islands could have been connected during the Ice Ages. However, the integration of genetics and bibliographic resources have been helping to clarify some populations.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Turkey||Present||Introduced||Ugurtas and Yildirimhan, 2000; Hur et al., 2008; Mollov, 2009; Ilgaz et al., 2013; Tok and Cicek, 2014; Tok et al., 2015||New locality: Samsun, Atakun|
|Libya||Present||Introduced||Arnold and Ovenden, 2002||Bengazi|
|Tunisia||Present||Introduced||Arnold and Ovenden, 2002|
|USA||Present||Present based on regional distribution.|
|-California||Widespread||Introduced||1994||Invasive||Deichsel et al., 2010||San Pedro, Los Angeles|
|-Connecticut||Widespread||Introduced||Donihue et al., 2014||Greenwich. First report in 2014|
|-Kansas||Present||Introduced||2004||Tucker, 1998; Taggart, 2004||Hays|
|-Missouri||Present||Introduced||2002||Briggler et al., 2015||Joplin|
|-New Jersey||Present||Introduced||1984||Burke, 2010||Local: Mt. Laurel|
|-New York||Widespread||Introduced||Gossweiler, 1975; Burke and Deichsel, 2008; Mendyk and Adragna, 2014; Goldfarb et al., 2016||First observation at Westchester in 2015|
|-Pennsylvania||Absent, formerly present||Introduced||1927||Burke and Deichsel, 2008||Locality: Philadelphia|
|Albania||Present||Introduced||Mizsei et al., 2016||Velipöje village (1995); 2 km Velipöje village (2015) ; Trush village (2015)|
|Croatia||Present||Introduced||Not invasive||Podnar, personal communication, 2013||Zagrev (city garden) Podnar, 2013 (pers. com.)|
|France||Present||Introduced||Morgue, 1924; Orsini, 1984; Bruekers, 2003; Corti, 2006||Hyeres, Côte d’Azur|
|Germany||Absent, formerly present||Introduced||Henle and Fritz, 2007||Schlossberg (castle hill), Freiburg and Offenbourg|
|Greece||Present||Introduced||2012||Adamopoulou, 2015||Palaio Faliro, Athens|
|Italy||Present||Introduced||Capula, 1994; Lo and Nicolini, 2001; Corti and Lo, 2002; Bruekers, 2003; Lever, 2003; Biaggini et al., 2009||Islands: Gallo Lungo and Santo Stefano|
|Portugal||Widespread||Introduced||1998||Gonzalez et al., 2001||Lisbon|
|Serbia||Widespread||Native||Gorman et al., 1975; Lever, 2003||Northern Serbia|
|Spain||Present||Introduced||Mertens and Wermuth, 1960; Meijide, 1981; Valverde, 2005; Valdeon et al., 2010; Rivera et al., 2011||Sant Celoni, Vllés Oriental (Barcelona). First observed in April 2011|
|-Balearic Islands||Localised||Introduced||Muller, 1905; Boulenger, 1920; Martinez-Rica, 1967; Perez-Mellado, 2009; Zawadzki and Seemann, 2009; Berg and Zawadzki, 2010||First found in Sant Jordi, Mallorca|
|Switzerland||Localised||Introduced||1980s||Hofer and Dušej, 1995; Schulte and Gebhart, 2011||Rapperswil|
|UK||Eradicated||Introduced||2010||Hodgkins et al., 2012||Buckinghamshire|
History of Introduction and SpreadTop of page
P. sicula introductions began in historical times within the Mediterranean basin and they continue currently to form a worldwide distribution.
Although there is a lack of understanding on the exact dates of introduction and the specific pathways of dispersal, the most common pathway was probably accidental by cargo due to maritime connections and trade between Italy and other islands.
During the 1800s, this species started to be introduced outside of the Mediterranean region. The first population reported in the USA was in Kansas in the 1950s and was followed by New York (1966), New Jersey (1984), California (1994) and Connecticut (2014). New locations within these states were found through the years, either by natural expansion of original native populations or by intentional/accidental releases of individuals to new areas (see History of Introduction and Spread table for details and references). In the USA it has become a popular pet, which has also resulted in intentional releases in private gardens or escapes from terrarium.
In Europe the history is different, with some historically introduced populations (e.g. Menorca during the Middle Ages) and others more recent (e.g. Albania – 1994/2015, Greece – 2012; UK– 2010, La Rioja – 2008/2009, Sant Celoni - 2011), a normal pattern due to the proximity of its native range. The Turkish populations seem to be in expansion within Marmara and Black Sea regions, with seven new localities found from 2000 until 2015. Another difference to the USA introductions is the main vector; in European populations accidental introductions by cargo and nursery trade prevails.
Studies from Silva-Rocha et al. (2012, 2014) and Kolbe et al. (2013) support a multiple source pattern of introductions, which makes P. sicula history complicated and difficult to address and, at the same time, justifies the ability of this species to spread and establish in new regions.
IntroductionsTop of page
|Introduced to||Introduced from||Year||Reason||Introduced by||Established in wild through||References||Notes|
|Natural reproduction||Continuous restocking|
|Albania||Hitchhiker (pathway cause)||Yes||Mizsei et al. (2016)||Not clear the origin of these populations, but it is more likely to be an accidental introduction by maritime traffic in Velipöje and then expansion to inland Trush|
|Balearic Islands||Italy||Hitchhiker (pathway cause)||Yes||Carretero and Silva-Rocha (2015); Silva-Rocha et al. (2012)|
|California||Sicily||1994||Pet trade (pathway cause)||Yes||Deichsel et al. (2010)||A person deliberately introduced four females and three males in his yard|
|Connecticut||New York||2014||Self-propelled (pathway cause)||Yes||Donihue et al. (2014); Donihue et al. (2015)||This population is a northern expansion of New York population. It used the railroad track as a way to disperse|
|France||Italy||Hitchhiker (pathway cause)||Yes||Bruekers (2003); Pascal et al. (2006)||Found in olive trees trunks|
|Germany||1913||No||Henle and Fritz (2007)||Populations now extinct probably due to habitat destruction or unfavourable climate conditions|
|Greece||Italy||2014||Hitchhiker (pathway cause)||Yes||Silva-Rocha et al. (2014)||Found in an artificial garden with imported trees|
|Italy||Italy||Biological control (pathway cause)
Hitchhiker (pathway cause)
|Yes||Biaggini et al. (2009); Bruekers (2006); Capula (1994)||Lizards were introduced in Gallo Lungo to control insect population. Padhenge population was found in 2004 in olive trees imported from southern Italy (Fogia)|
|Kansas||Italy||1950s/2004||Escape from confinement or garden escape (pathway cause)
Pet trade (pathway cause)
|Yes||Taggart (2004); Tucker (1998)||Pet Trade/Escape|
|Missouri||Kansas||2001||Escape from confinement or garden escape (pathway cause)||Yes||Briggler et al. (2015)||Accidental introduction. Individuals were collected in Topeka (Kansas) and placed in a terrarium that was overturned by a feral cat, allowing lizards to escape|
|New Jersey||Italy||1984||Pet trade (pathway cause)||Yes||Burke (2010); Kolbe et al. (2013)||Adriatic Coast: A resident of Mt Laurel released 120 lizards from a Bronx commercial importer/dealer|
|New York||Italy||Pet trade (pathway cause)||Yes||Burke and Deichsel (2008); Kolbe et al. (2013)||Escapes from pet wholesalers, collection for pets and spreading by railroads are the main pathways of spread|
|Pennsylvania||1927||Pet trade (pathway cause)||No||Burke and Deichsel (2008)||Multiple escapes from a pet wholesaler|
|Spain||Italy||Hitchhiker (pathway cause)||Rivera et al. (2011); Silva-Rocha et al. (2012)||Both Almería and Cantabria populations transported via Italian troops during the Spanish Civil War. Both La Rioja and Sant Celoni populations were found in olive trees|
|Switzerland||1980s||Yes||Schulte and Gebhart (2011)||Lizards were found close to a zoo, near a local railway station. It is not clear if introduction was intentional or accidental with cargo|
|Turkey||Italy||2007||Hitchhiker (pathway cause)||Yes||Mollov (2009); Silva-Rocha et al. (2014)||Accidental introduction to Mudanya by people or merchant vessels|
|Turkey||Italy||1999||Hitchhiker (pathway cause)||Yes||Silva-Rocha et al. (2014)||Accidental introduction to Mudanya by people or merchant vessels|
|Turkey||Hitchhiker (pathway cause)||Yes||Ilgaz et al. (2013); Tok and Cicek (2014); Tok et al. (2015)||Accidental introduction to Filyus (Zonguldak), Atakum (Samsun), Çanakkale (Gelibolu) by people or merchant vessels|
|UK||Italy||2010||Hitchhiker (pathway cause)||No||Hodgkins et al. (2012); Silva-Rocha et al. (2012)||Lizards were transported in a consignment tufa imported from Italy for a garden restoration. Early detection allowed for successfull erradication|
Risk of IntroductionTop of page
P. sicula is an opportunistic lizard, capable of adapting to a range of habitats, often inhabiting humanized areas and using man-made objects or ornamental plants as refuges. Therefore, risk of its accidental transportation is high, and the availability of an anthropic environment seems important for its spread (Corti and Lo Cascio, 2002).
Another risk factor is that the Italian wall lizard seems to be popular as a pet, especially in the USA. Several websites promote the adoption of this species and care sheets can be found containing all the information needed to maintain the animal in captivity. It is important to note that introductions of animals generally due to the pet trade have been growing since the 1970’s, almost exponentially; indeed, the pet trade is the main pathway by which amphibians and reptiles are being introduced (Kraus, 2009).
HabitatTop of page
P. sicula can be found in a wide range of habitats; from natural grassy areas, scrublands meadows, roadside verges and coastal dunes, to agro-environments, pine plantations, parks and gardens, urban areas, stone walls and buildings (Capula, 1994; Oliverio et al., 2001; Biaggini et al., 2006; Corti, 2006). It normally inhabits areas below 1000 m, however, it is able to reach 2000 m (Arnold and Ovenden, 2002).
Habitat ListTop of page
|Terrestrial – Managed||Cultivated / agricultural land||Secondary/tolerated habitat||Natural|
|Managed forests, plantations and orchards||Secondary/tolerated habitat||Natural|
|Disturbed areas||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Disturbed areas||Secondary/tolerated habitat||Natural|
|Rail / roadsides||Secondary/tolerated habitat||Natural|
|Urban / peri-urban areas||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Urban / peri-urban areas||Secondary/tolerated habitat||Natural|
|Buildings||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Terrestrial ‑ Natural / Semi-natural||Natural grasslands||Principal habitat||Natural|
|Rocky areas / lava flows||Principal habitat||Harmful (pest or invasive)|
|Rocky areas / lava flows||Principal habitat||Natural|
|Scrub / shrublands||Principal habitat||Harmful (pest or invasive)|
|Scrub / shrublands||Principal habitat||Natural|
|Coastal areas||Principal habitat||Harmful (pest or invasive)|
|Coastal areas||Principal habitat||Natural|
|Coastal dunes||Principal habitat||Harmful (pest or invasive)|
|Coastal dunes||Principal habitat||Natural|
Biology and EcologyTop of page
This species is oviparous and has a seasonal reproductive cycle every year. In its native range (and similar latitudes), the mating season starts in March and can last until July. Egg deposition in females occurs from May to June, and eggs are spawned in clutches. If not breeding for the first time, females may lay up to 4 or even 5 clutches (each clutch can contain 2-12 eggs, but the normal range is 5-6) (Salvador, 2006; Corti, 2006). Eggs normally hatch in 5-7 weeks and offspring typically measure 3-3.5 cm from snout to vent (Arnold and Ovenden, 2002).
Egg laying can vary between island and mainland populations. Small island populations of north Croatia lay fewer eggs (2-4) compared to mainland ones but eggs are larger and hatch into larger offspring, often with shorter legs (Arnold and Ovenden, 2002). This strategy seems to be advantageous to islet conditions (few predators and low availability of food).
Maturity is usually reached when offspring are about 5 cm from snout to vent. For males this is usually after 1 year and for females it can be 1-2 years.
Physiology and Phenology
A study of thermal requirements using Southern California populations (Liwanag et al., 2016) concluded that thermal tolerance varies with age and gender. Females were shown to have a wider thermal breadth than males and juveniles, and able to tolerate colder temperatures. However, adults in general were found to be capable of tolerating higher temperatures than juveniles (Liwanag et al., 2016).
Lizards from Long Island (New York, USA) are subject to much colder winters than they would be in their native range near Rome. Winter temperatures there can reach -7ºC; while in Long Island temperatures can reach -20ºC. Although this is a huge difference, animals are able to survive and even expand to northern locations in the USA. Burke et al. (2002) suggest that survival to these conditions is most likely due to hibernation deep underground, where they can avoid freezing. P. sicula is able to tolerate colder temperatures by supercooling, but it cannot survive for long if ice nucleation occurs; burrowing themselves 24 cm deep will allow them to pass the winter. Nevertheless, hibernacula places are still not known.
Herrel et al. (2008) and Vervust et al. (2010) studied morphological and physiological adaptation of P. sicula in two islands off the Adriatic coast (Pod Mrcaru and Pod Kopiste). These two islands were part of an experimental introduction in the 1970’s (Nevo et al., 1972), in which five pairs of P. sicula were introduced from Pod Kopiste (only inhabited by P. sicula) to Pod Mrcaru (only inhabited by P. melisellensis), and five pairs of P. melisellensis were translocated from Pod Mrcaru to Pod Kopiste. It is important to note that P. melisellensis got extinct from Pod Mrcaru. Both islands represent introduced populations of Italian wall lizard and provide a unique opportunity to study adaptive evolution in a short period of time. Hence, Herrel et al. (2008) and Vervust et al. (2010) took advantage of this history to look at the changes at a morphological and physiological level. They concluded that Pod Mrcaru lizards feed on a greater proportion of plant material which could have led to several adaptations: (i) head dimensions and bite forces are higher in Pod Mrcaru (to help tear up tough plant material); (ii) presence of cecal valves in hindgut on Por Mrcaru lizards (to slow down food passage and provide fermenting chambers); (iii) Pod Mrcaru individuals have longer and more complex intestines (to increase digestive efficiency); (iv) Pod Mrcaru lizards have wider, broader and stronger teeth (to facilitate tear of rough plant material); (v) nematodes were present in Pod Mrcaru but not in Pod Kopiste. Vervust et al. (2010) also did an experiment where lizards of Pod Mrcaru were fed only with arthropods over the course of 15 weeks to assess if adaptation was mainly genetic or plastic. They suggest that at least some of the changes are based on plastic adaptation, since after the experiment the digestion tract length was reduced and a total loss of cecal valves was observed. These experiments provide an excellent understanding on the ability of P. sicula to adapt in new environments, and has revealed a digestive flexibility that can be advantageous to its establishment and colonization success.
Monti et al. (2013) performed a study on individuals from mainland and Licosa Island, where lizards present in the latter were darker (i.e. increased expressiveness of melanocortins). They concluded that this physiological process was associated to an increase in reproductive effort and a better resistance to parasites during the breeding season.
In its native range, P. sicula is diurnal and active all year, although during the winter, activity can decrease and only some individuals are seen on sunny days (Corti, 2006). Daily activity is mainly unimodal, with the exception of the summer season when soil temperatures exceed 40ºC. At this temperature, lizards are typically active morning and late afternoon (bimodal) reducing their locomotor activity and can be seen taking refuge in shade or burrows to avoid overheating (Foà and Bertolucci, 2001).
In contrast, in their introduced range in New York, USA, lizards are not active from November to February, and only seen in high numbers from May to August. Their daily activity is similar to in their native range, with unimodal pattern almost all of the active months and bimodal patterns from June to August. In general, they are less active during the year in New York but also active fewer hours per day when active, compared to their native range.
Population Size and Structure
In its native range, P. sicula can be found in high numbers and populations are large. Even when inhabiting low productivity ecosystems (such as vineyards) they can retain large populations as they are able to exploit a large variety of prey (small arthropods) (Biaggini et al., 2009).
In their introduced range, populations are equally dense but the capability to expand may be less so. In Cantabria, for example, the population is constrained to the same place that it was initially introduced to, even though it is a dense population. Other introduced populations (USA, Lisbon, Menorca) represent cases where populations are highly dense and able to expand their territory.
P. sicula diet can vary depending on geographical position, ecological conditions (i.e. mainland or island), season or local prey fauna composition. The main composition is arthropods, however when arthropods are scarce they are able to incorporate small molluscs, crustaceans, plant matter, small reptiles (even cannibalism) and small mammals. They are very plastic and capable of adapting to different diets.
The percentage of each food material can vary with population, even within its native range (Zuffi and Giannelli, 2013). For example, in central Italy (around Rome) Isopoda represent 50% of the prey items, followed by Leptidora, Coleoptera and Gasteropoda. While in Luca (northwestern part), Coleoptera represent 30% of prey, followed by Insects, Araneae, Othoptera and Hemiptera. Diet composition is even more variable between introduced populations, specifically those from the USA (Burke and Mercurio, 2002; Zuffi and Gianneli, 2013) and the studied Croatian island population which is mainly plant-based (Herrel et al., 2008; Vervust et al., 2010).
The Natural Sources table provides further details on nutrition as found by Zuffi and Giannelli (2013).
Natural Food SourcesTop of page
|Food Source||Food Source Datasheet||Life Stage||Contribution to Total Food Intake (%)||Details|
ClimateTop of page
|BS - Steppe climate||Tolerated||> 430mm and < 860mm annual precipitation|
|Cf - Warm temperate climate, wet all year||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
|Cs - Warm temperate climate with dry summer||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
|Cw - Warm temperate climate with dry winter||Tolerated||Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)|
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Notes on Natural EnemiesTop of page
The main predators of the Italian wall lizard are birds, snakes and feral cats.
Means of Movement and DispersalTop of page
P. sicula, like many lizards, has limited mobility. However, with globalization, non-natural dispersal started to occur at high rates, allowing the species to reach a worldwide distribuition.
Once introduced to new areas, P. sicula may naturally disperse, expanding their range even further.
P. sicula uses trees, plants and man-made structures as refuges so most of the European introductions have occurred due to accidental introduction by cargo, ornamental trees or other materials (Silva-Rocha et al., 2014). The nursery trade (i.e. olive trees) is in fact the most worrisome pathway nowadays, since it can introduce several species at once (Rivera et al., 2011).
In the USA, most of the introductions have been deliberate and linked to the increasing pet trade. However, after population establishment, lizards start to disperse naturally across railways and other potential barriers, expanding their range.
Impact SummaryTop of page
Environmental ImpactTop of page
Impact on Biodiversity
Currently, the only recorded impacts of P. sicula have been on native lizards in areas where P. sicula has been introduced. These impacts include endemic species as well as the critically endangered Aeolian wall lizard, Podarcis raffonei, and the endangered Lilford's wall lizard, Podarcis lilfordi (Capula, 2006). Behavioural interference was shown with the lizard Podarcis melisellensis (Downes and Bauwens, 2002), which has now gone extinct on the Adriatic Islands after the introduction of P. sicula (Nevo et al., 1972); where the Italian wall lizard competed not only for diet resources, but also for basking and refuge sites.
It is also reported as affecting the critically endangered Aeolian wall lizard P. raffonei, reducing its range and causing extinction of most of its populations (Capula et al., 2002). As well as displacement, there is also evidence of possible hybridization between the two species as electrophoretic alleles of P. raffonei have been found in individuals of P. sicula from Lipari Island (Capula, 1994). This suggests that in the past these two species hybridized with introgression which could have caused the extinction of the former on the island. Hybridization can cause the loss of distinctive characteristics of native species or even virtually eliminate them through genetic swapping (Riley et al., 2003). Furthermore, once the ‘pure’ genotype is lost there is no way to recover it, contrary to merely ecological impacts, like habitat modification for example, which still allows for restoration. It is important to note that P. raffonei is the most endangered lizard species in Europe.
In the USA some impacts are recognized. In California, P. sicula has dietary overlap with native lizard species (Sceloporus occidentalis and Elgaria miulticarinata) and may also have predatory impacts (Kirschbaum and Pauly, 2016). In Kansas, there is possible competition with native lizards (Plestiodon obsoletus) (Oliverio et al., 2001).
Impacts on the invertebrate community are not known.
Threatened SpeciesTop of page
|Threatened Species||Conservation Status||Where Threatened||Mechanism||References||Notes|
|Elgaria miulticarinata||LC (IUCN red list: Least concern) LC (IUCN red list: Least concern)||Competition - monopolizing resources; Predation||Kirschbaum and Pauly, 2016|
|Podarcis lilfordi||EN (IUCN red list: Endangered) EN (IUCN red list: Endangered)||Balearic Islands||Competition - monopolizing resources; Competition - shading|
|Podarcis melisellensis||No Details||Competition - monopolizing resources||Downes and Bauwens, 2002|
|Podarcis raffonei||CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered)||Italy||Competition - monopolizing resources; Competition - shading; Hybridization||Capula et al., 2002|
|Podarcis tiliguerta||LC (IUCN red list: Least concern) LC (IUCN red list: Least concern)||Hybridization||Capula et al., 2002|
|Podarcis wagleriana||LC (IUCN red list: Least concern) LC (IUCN red list: Least concern)||Hybridization||Capula, 1993|
|Sceloporus occidentalis||LC (IUCN red list: Least concern) LC (IUCN red list: Least concern)||Competition - monopolizing resources; Predation||Kirschbaum and Pauly, 2016|
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Has a broad native range
- Abundant in its native range
- Highly adaptable to different environments
- Is a habitat generalist
- Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
- Capable of securing and ingesting a wide range of food
- Benefits from human association (i.e. it is a human commensal)
- Fast growing
- Has high reproductive potential
- Has high genetic variability
- Negatively impacts animal health
- Reduced native biodiversity
- Threat to/ loss of endangered species
- Threat to/ loss of native species
- Negatively impacts animal/plant collections
- Competition - monopolizing resources
- Competition - shading
- Interaction with other invasive species
- Rapid growth
- Highly likely to be transported internationally accidentally
- Highly likely to be transported internationally deliberately
- Highly likely to be transported internationally illegally
- Difficult to identify/detect in the field
- Difficult/costly to control
UsesTop of page
In the USA, P. sicula has become of value to the pet trade.
P. sicula has been used as a research model in several ecotoxicological experiments, due to its wide distribution (on both the mainland and islands), diversity of habitats, limited mobility, mainly insectivorous diet and locomotion on the soil surface (it can be affected by contaminants).
DiagnosisTop of page
Several phylogeographic studies were published with Cyt-b marker (Podnar et al., 2005; Kolbe et al., 2013; Silva-Rocha et al., 2012, 2014). Therefore, this marker can be safely used to make a genetic diagnosis of the species.
Detection and InspectionTop of page
It can be difficult to distinguish P. sicula in the field if other similar species are present. Its morphology can be very variable, and dependent on location but Arnold and Ovendem (2002) providefull descriptions on regional variations.
Similarities to Other Species/ConditionsTop of page
The Italian wall lizard can be easily confused with the common wall lizard (Podarcis muralis). However, P. sicula can be distinguished by the absence of dark spots on its ventral side, one of the main characteristics of P. muralis (at least on the throat). The dorsal patterns on both lizards are also quite different.
Another similar species is the Sicilian wall lizard (P. wagleriana). Usually, P. sicula has a more reticulated dorsal part but individuals from both species can be found with no pattern. In this case, the best way to distinguish one from the other is to check if the belly has a bright colour, if the head is deeper and the body shape more graceful; if so, then the species is P. wagleriana and not P. sicula.
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
P. sicula has been introduced from distinct sources and pathways over time. There have been multiple independent events of introductions and the actions taken should be more global and preventative. This prevention could be done by implementing inspection and quarantine measures of commercial cargo and trade, since these two means are the main pathways of introduction. The pet trade of this species, particularly in the USA, should ideally be made illegal. Additionally, public awareness could be enhanced to highlight the impacts resulting from the release of this species and other alien species into the wild.
Special prevention should be carried out to avoid translocations of the Italian wall lizard to islands and islets, namely from Menorca to surrounding islets where endemic P. lilfordi is present and from Lisbon to the Canary Islands, Madeira or Azores.
Eradication programs have already been implemented and deemed successful in some populations, such as La Rioja (Valdeón et al., 2010) and in the UK (Hodgkins et al., 2012). Another localized population in Noja (Cantabria) has the potential to be eradicated successfully. In the USA, populations recently detected could also be eradicated with success, potentially, but older well established populations are too widespread. Early detection is key for truly successful eradications.
In most populations, controlling the population size (and so avoiding its expansion) by catching the maximum number of individuals possible is the only measure available.
Monitoring and Surveillance (Incl. Remote Sensing)
In order to prevent the dispersal of the species to vulnerable habitats, close monitoring of the populations is advisable.
Gaps in Knowledge/Research NeedsTop of page
It is important to assess the demographic status and spatial distribution of the introduced populations, as well as continuing with research to understand and establish factors which may limit or promote successful establishment. Further studies on biodiversity impacts are also needed, not only on native lizard species, but also on invertebrate communities.
ReferencesTop of page
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ContributorsTop of page
16/05/16 Original text by:
Iolanda Rocha, CIBIO-inBiO, Portugal
Distribution MapsTop of page
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