Podarcis muralis

Aside from differences in colour, the morphs vary by length, survival rate, and immune resistance/response to infection.[14]

Podarcis muralis photographed at Mosel valley (Germany)

Susceptibility to infection also varies between morphs, red and yellow-red morphs are the most susceptible to infection by the haemogregarine parasite, a common parasite for these lizards. White morphs are the most resistant to this parasite and the yellow morphs are at an intermediate value of immune resistance and intensity.[14] Certain traits can also lead to a variation in snout-vent length in each of these morphs.[14] For example, in orange morphs, sexual selection favours larger morphs which makes them, on average, larger than the other morphs.[14]

The femoral gland secretions of males differ in chemical composition according to each respective morph.[16] Secretions are used by males for intra-species communication, such as marking of territories and attracting potential mates. Individuals share the same organics within the secretions, but the concentrations of certain key compounds differ. For example, α-tocopherol is present in higher concentrations in the secretions of red morphs.[16] This molecule allows for scents to remain in the environment longer by reducing the rate of oxidation in humid environments.[17] This indicates that red morphs tend to be more territorial and maintain territories for longer periods of time compared to other morphs. This phenomenon is also seen when it comes to the age of lizards. Similarly, older, more territorial lizards have higher levels of α-tocopherol compared to younger individuals who are more prone to roaming regardless of morph.[16] Again, indicating that the composition of the secretions relate to the function. Furanones are found in higher concentrations in white morphs, followed by yellow, then red morphs.[16]

Among females, reproductive strategies differ by morph; yellow females are r strategists, producing many smaller eggs in their clutch which would allow for numerous offspring to be produced and proliferate in smaller populations with less competition.[18] White females are K strategists, producing fewer, larger eggs which makes offspring more likely to survive in harsher, more competitive environments.[18] Red females can be r or K strategists based on the environment they are in.[18] The existence of alternate strategies points to how morphs have adapted to different environments and hints to the maintenance of colour polymorphism as with fluctuations in environments each morph will eventually be the fittest and as such will not be selected out of the population.

The differences observed between morphs are unique evolutionary trade offs employed by each morph to promote survival within the different environments they face in light of limited ability to adapt perfectly to each pressure. Such a trade off is seen when comparing orange morphs to white morphs: morphs, on average, have larger body sizes compared to the white morphs but, in exchange, they are more prone to parasitic infection.[14] In orange morphs, more emphasis is placed on being larger and having the ability to physically compete and ward of potential threats, but in white morphs, metabolic emphasis is placed on having a more hardy immune system to resist infection. Again, these trade offs can arise as there are selective differences in the environment each morph prefers. The differences in the relative proportions of the morphs with respect to location show that environmental pressures differ and some morphs' trade offs are more successful in specific environments than another's.[4]

Podarcis muralis has been introduced in the United States and is spreading throughout the Cincinnati metropolitan area. It is commonly observed living in limestone outcrops, rock walls, and rubble along the Ohio River basin.[21]

Podarcis muralis photographed in Cincinnati, Ohio - 2015.

It is referred to locally in the Cincinnati/Northern Kentucky area as the "Lazarus lizard",[22] as it was introduced to the area around 1950 by George Rau, a boy who was a member of the family who owned the Lazarus department store chain (now absorbed into Macy's). After he returned from a family vacation to northern Italy, he released about 10 of the reptiles near his Cincinnati home.[23] Genetic testing has revealed that as few as only three of these lizards survived long enough to reproduce, meaning they were subject to an extreme genetic bottleneck.[24] This prolific lizard has reproduced exponentially; it continues to expand its distribution range annually, and has established itself so well in southwest Ohio, it is now considered a naturalized species by the Ohio Department of Natural Resources and is protected under state law (it is illegal to harm, capture, or possess this animal without a proper licence).[25]

Besides Ohio, P. muralis has also been introduced in other U.S. states. Populations occur in Kenton and Campbell counties in Kentucky, and in parts of Indiana.

The European wall lizard was also introduced to Vancouver Island, British Columbia, Canada in 1970, when a dozen individuals were released into the wild from a small private zoo.[26]