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| Pair; female (left) and male (right) of Podarcis erhardii ruthveni sharing the same thermoregulation spot (Picture: Stamatis Kalogiannis) |
Inroduction
The Erhard's wall lizard (Podarcis erhardii; Bedriaga 1882) is one of the most widespread lacertid species in Greece, with a range covering most of the mainland and several Aegean islands and islets, including tiny rocky outcrops with almost zero vegetation. Due to the complex paleogeographic history of the Aegean, the dispersion and isolation of Podarcis erhardii populations within the region has resulted to notable geography-related variation in morphology, phylogeography, habitat selection, behavior and even feeding habits among different insular populations. Although the species is the most extensively studied Greek reptile and is represented by dozens of described subspecies in Greece, the phylogenetic relations of P. erhardii demand further research – future studies might shed light into this lizard's taxonomy and lead to the description of new taxa. Overall, this common but beautiful small lacertid can be described as a wonderful product of evolutionary history and has served as significant living proof of insular evolution.
Description
TL; ~22cm, SVL; Commonly up to 7,5cm or more, some insular populations may be larger. Very wide color variation throughout its range; dorsal coloration usually brown, olive or bright green, depending on locality/subspecies, habitat and time of the year – usually more greenish during the winter. Neck and abdomimal area typically pale white outside the breeding season, but both sexes (especially males) typically exhibit very bright colors during breeding or at random times throughout the year, including intense red, orange or yellow in the neck and ventral area, as well as blue or yellow outer ventral scales on the flanks. Lateral area typically dark brown. Females with light dorsolateral stripes, which are either less defined or absent in males. Males typically exhibit dark reticulated pattern with light spots on the flanks and dorsal area. Also, note that males are usually larger than females, with heavier heads in comparison to the body; females appear to be more elegant, with small heads and a more flattened body. Two broad dark bands often run across the sides of the dorsal area, which are wider and more defined in females of P. e. livadiaca; males of the same subspecies often show a very distinct golden or silver coloration. On the other hand, most Cycladic populations have an intense green coloration, while subspecies riveti and ruthveni are usually brown, olive or greyish. Uniform (concolor) individuals, lacking any dorsal or lateral pattern, are rather frequent. May be confused with the Common wall lizard Podarcis muralis on the mainland, but note that Podarcis muralis often has a dark vertebral line which typically lacks in P. erhardii. Also, the latter usually occupies more dry enviroments in lower altitudes.
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| Male with breeding colors, subspecies livadiaca, Euboea (C) Stamatis Kalogiannis |
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| Male, subspecies livadiaca, Euboea (C) Stamatis Kalogiannis |
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| Female, subspecies livadiaca, Attica (C) Ioannis Gourogiannis |
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| Male, subspecies livadiaca, Euboea (C) Plato Stefanopoulos |
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| Female, subspecies livadiaca, Euboea (C) Plato Stefanopoulos |
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| Male, subspecies mykonensis, Tinos island (C) Ioannis Gourogiannis |
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| Female, "Santorini population" (C) Charis Kouelis |
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| Female, "Santorini population" (C) Charis Kouelis |
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| Female, subspecies riveti, Pieria (C) Charis Kouelis |
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Female with breeding colors, subspecies ruthveni, Alonissos island (C) Stamatis Kalogiannis |
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| Young male, subspecies ruthveni, Alonissos island (C) Stamatis Kalogiannis |
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| Female, subspecies ruthveni, Alonissos island (C) Stamatis Kalogiannis |
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| Male, subspecies ruthveni, Alonissos island (C) Stamatis Kalogiannis |
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| Male, subspecies ruthveni, Alonissos island (C) Stamatis Kalogiannis |
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| Female, subspecies ruthveni, Alonissos island (C) Stamatis Kalogiannis |
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| Female, subspecies ruthveni, Alonissos island (C) Stamatis Kalogiannis |
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| Female, subspecies ruthveni, Kyra Panagia islet (C) Stamatis Kalogiannis |
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| Female, subspecies ruthveni, concolor morph, Alonissos (C) Stamatis Kalogiannis |
Habitat
Generally favours rocky but lush areas with openings, but inhabits any available habitat type on islands, including forests, olive groves, gardens, phrygana, maquis, riparian zones and beaches. Rather scarce on the mainland, where it occupies open and sunny areas. Very dense populations can be observed on stonewalls on Aegean islands, as well as on tiny, rocky islets with Pistacia shrubs and low phrygana. Tolerates extremely xeric conditions. Up to 1,400 m asl.
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| Oak forest at 700m asl – habitat of Podarcis erhardii livadiaca |
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| Section of a perennial stream surrounded by rocky terrain – habitat of Podarcis erhardii livadiaca |
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| Dry slope with low phrygana and maquis – habitat of Podarcis erhardii ruthveni |
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| Stonewall covered by Smilax aspera in an agricultural area – habitat of Podarcis erhardii ruthveni |
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| Stonewall covered by ferns and bushes in a humid, agricultural area – habitat of Podarcis erhardii ruthveni |
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| Forest opening – habitat of Podarcis erhardii livadiaca |
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| Xeric coastal phrygana – habitat of Podarcis erhardii mykonensis |
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| Open grove on a dry, rocky hill – habitat of Podarcis erhardii mykonensis |
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| Perennial stream – habitat of Podarcis erhardii livadiaca |
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| River mouth of a perennial stream bordering phrygana – habitat of Podarcis erhardii livadiaca |
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| Roadcut with maquis and open Pinus halepensis forests – habitat of Podarcis erhardii livadiaca |
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| Low vegetation on a small, rocky islet – habitat of Podarcis erhardii ruthveni |
Biology
Erhard’s wall lizards are typical members of the genus Podarcis. Hence, their biology has many parallels with other species in the genus. P. erhardii brumates underground, though in most areas, especially in lower altitudes, it is active throughout the whole year and brumation is not continuous. While it is not as cold-tolerant as Podarcis muralis, it is not uncommon to observe individuals basking in chilly temperatures, as long as there is sunshine. They also seem to be considerably heat-tolerant, however, extreme heat usually equates to inactivity. They are mostly ground-dwelling, though they frequently climb structures such as rocks, stone walls or fallen logs to bask. Like most lacertids, males are highly territorial and will fight rival males off their territory, often resulting in fatal injuries. Reproduction takes place from February to June, with the peak season usually being April and May. Clutch size ranges from 1-5 eggs which take approximately 40 days to hatch. Fresh hatchlings can be observed throughout the summer season (June to September), but they peak around mid-August. It is mainly an arthropod-eating lizard, with a preference for relatively large insects, though like most other lacertids, its diet can vary greatly and shift according to food availability. This can be influenced according to season or the type of habitat, among other factors. Consumption of plant matter, including fruit that has been discarded by humans seems to be commonplace, especially in small insular populations. There generally seem to be considerable differences between the diet of populations on islands compared to those in the mainland. Cannibalism is a common habit on small islets where food availability is very low. Furthermore, an interesting case of symbiosis between Erhard's wall lizards and Eleonora's falcons takes place on Aegean islets, where lizards often feed on prey leftovers or insects attracted to excrement and perhaps on external parasites of the chicks. Erhard’s wall lizards, like most lacertids, can perform caudal autotomy if a potential predator grasps them from the tail. The tail will be regenerated; however, it will not match the size and pattern of the original. P. erhardii are also incredibly fast-moving and that constitutes their main defense against predators. However, unlike Lacerta, they seem to be more daring and curious, and while they will instantly retreat to a refuge if approached, if no noise or other disturbance is produced, they will quickly come out of their refugium to investigate, and they can often be approached within a few centimeters. Pairs of males and females often bask together taking advantage of the same thermoregulation spot, however wihout any indication of pair bond outside the breeding season, since the same phenomenon has been observed with lizards sharing a basking spot with species from completely different families.
Distribution
Widespread throughout mainland Greece, though with a rather scattered distribution. Absent from the westernmost parts of the mainland and from most of the Peloponnese, except for the northeastern part of the peninsula. Occurs on several Aegean islands west of the mid-Aegean trench; Euboea, Samothrace, Hydra, all of the Northern Sporades islands and islets (except Skiathos, Piperi and Skyros archipelago), most of the Cyclades archipelago (e.g. Andros, Tinos, Naxos, Paros, Syros, Mykonos, Ios, Sikinos, Amorgos, Santorini, Folegandros, Anafi, Koyfonisia, Iraklia, Sifnos, Serifos – absent from the Milos archipelago) and on a few of the westernmost Dodecanese islands (e.g. Astypalea and surrounding islets).
Throughout the years, a total of about 20 subspecies have been described from Greece; however, most are considered invalid and have been synonymized. We recognise the following subspecies / populations until further taxonomic revisions:
- Podarcis erhardii riveti: most of mainland Greece, Samothrace. Doubtful reports (mentioned as thessalica) exist from Euboea.
- Podarcis erhardii livadiaca: SE mainland Greece (Boeotia, Attica), NE Peloponnese, Hydra isl., all of Euboea
- Podarcis erhardii ruthveni: Northern Sporades
- Podarcis erhardii naxensis: Naxos, Paros, Iraklia, Ios, Folegandros, Donoussa, Sikinos, Schinoussa and surrounding islets
- Podarcis erhardii mykonensis: Andros, Tinos, Mykonos, Syros, Delos
- Podarcis erhardii thermiensis: Kythnos
- Podarcis erhardii amorgensis: Amorgos, Keros, Koufonisia (?), Anafi (?)
- Podarcis erhardii syrinae: Astypalea and surrounding islets
- Podarcis erhardii erhardii: Serifos, Sifnos
- Santorini population: The systematic status of P. erhardii populations from Santorini and surrounding islets remains unclear; Werner (1938) places these populations to naxensis, while Frör & Beutler (1978) place them to mykonensis. Genetic data shows that the lizards of Santorini originate from Andros and Anafi. Nevertheless, Podarcis erhardii from Santorini show intermediate morphological characters, which are far from typical naxensis.
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Approximate distribution of Podarcis erhardii subspecies in Greece
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