The first time that I saw a Wall Lizard in Cincinnati, it was only for an instant as it ran across the walkway in front of me. But I saw enough of it to realize it was a lacertid, and that stopped me in my tracks as I thought, “What the heck is THAT doing here?” There are no lacertid lizards native to North America. So I figured it must have been a pet that escaped or was released. But then I saw more of them. And still more. Realizing that there must be an entire population of them here, I went searching online, and found the “Lazarus Lizard".
The Common Wall Lizard, Podarcis muralis, is, as the name implies, a familiar sight in most of southern Europe from Spain to Turkey. A greenish ten-inch lizard with a long tail and a pointed snout, the Wall Lizard likes to be around human cities and is seldom found far away from buildings, parks or parking lots. It makes its home in stone walls, rock piles, construction rubble, or among ancient Roman ruins.
For biologists, the lizard is interesting because it seems to be in the process of speciation—of dividing itself into a number of different species. Within its wide geographic range, the reptiles encounter a variety of climatic and ecological conditions, and the populations in each area have adapted themselves to their own particular circumstances. To the human eye, the most noticeable difference is color: some individuals of Wall Lizard throughout their range have greenish scales on their backs, and others have grayish or brownish. More significantly, however, are the color differences that seem to separate them into distinct geographic regions: some local populations have reddish scales on their bellies, some have yellowish, and some have white.
But there are other genetic differences associated with these color variations which are, in the evolutionary sense, much more important. The reddish “morphs” tend to be the largest, reaching up to ten inches. The males of all Wall Lizards have special pores on the inside of their thighs that produce chemicals called tocopherols for marking their territory and attracting females, but the chemical markers found in the reddish-bellied populations tend to be stronger and longer-lasting than those of the yellow morphs. The white-bellied males, by contrast, have low levels of tocopherols but a higher concentration of different chemicals called furanones.
The various populations also differ in their reproductive strategy. Females in yellow-bellied areas tend to lay a larger number of smaller-sized eggs: white-bellied females, by contrast, tend to produce smaller clutches of larger eggs, while the females in areas where red bellies predominate seem to be able to vary their clutch and egg size according to local conditions.
Another interesting variation deals with resistance to parasites. Wall Lizards are often infected by a group of microscopic blood parasites called haemogregarines. But the white-bellied populations seem to exhibit a distinctly higher level of resistance to this infection, while the red-bellied morphs seem to be particularly vulnerable.
Overall, then, each of the color morphs seems to be settling on a dissimilar set of characteristics which gives them different ecological advantages and disadvantages. The red morph for instance is larger and stronger on average, but is more vulnerable to parasites. The white morph, by contrast, is smaller but is more resistant to parasites, and because it is hardier it is able to lay fewer eggs and still maintain its population. The white-bellied lizards are also emphasizing a different pheromone chemical as their sexual attractant and territorial marker, which will likely over time make them unattractive to the other versions, reproductively isolating that population into its own separate gene pool. In other words, a new species. Each of the different color morphs, indeed, seems to be on its way to separating from the others and claiming its own ecological niche as a new species.
Which brings us to Cincinnati ….
There are a lot of Wall Lizards in Cincinnati. Really a lot of them: it is estimated that good habitat areas have as many as 1500 lizards per acre, and there are probably in excess of a million of them living within the city limits.
For decades, no one was really sure how they first got here. In one tale, a returning soldier from the Second World War brought some back with him. In another version, a boy who had been on vacation in Switzerland kept a few as pets. Another story has the prominent Lindner family inadvertently introducing them in potted plants they got during a trip to Florida.
Then in 1989, the mystery was solved. George Rau was, in 1951, the 10-year old stepson of Fred Lazarus III, a member of the well-known family which founded the Lazarus chain of department stores in Ohio (they later merged with Macy’s). During a family vacation to Lake Garda in northern Italy (not very far from Milan), Rau recalled, he had managed to capture ten of the elusive little lizards and brought them back to the USA with him, wrapped inside a sock in his luggage. He released them into the family backyard in East Walnut Hills, and the lizards took it from there.
And genetic analysis confirmed the story. The DNA of Cincinnati’s population maps to that of the reddish-bellied Wall Lizards of northern Italy. Also, the Cincinnati lizards have their greatest genetic diversity in the East Walnut Hills area (now known informally by city residents as “Lizard Hill”), indicating that they have been living there the longest. Since then, Cincinnati’s Wall Lizards have become known to locals as “Lazarus Lizards”.
But remarkably, the Cincinnati lizards do not differ from their European ancestors in name only. Biologists who study them have found that the Ohio population is itself evolving. They tend to have longer legs and stronger limb muscles than their Italian ancestors—perhaps an adaptation to the more vertical surfaces of downtown urban life. DNA sequencing has shown that not all of 10-year old George Rau’s lizards seem to have survived the wilds of Cincinnati: all of the city’s current population of over a million is descended from just a tiny number, perhaps as low as three, of reproducing individuals. This produced what geneticists call a “founder effect”, in which a population is greatly reduced in genetic diversity because of the small gene pool found in its initial members. Despite this, however, Cincinnati’s lizards have already, in the space of 60 years (about 35-40 generations), evolved a number of new genes that are not found in the ancestral European lizards. Because of this genetic distinctiveness, it has been proposed to classify the Ohio population as a different subspecies from the European Wall Lizard, and the Latin name Podarcis muralis maculiventris has been proposed for the Lazarus Lizard.
Cincinnati, meanwhile, has adopted their local lizard as a sort of mascot. Although it is a non-native species and a potential invasive, and nobody really knows what effects it may have on the three local species of native lizards, the Lazarus Lizard is legally protected by the state of Ohio, and nobody may harm one or keep it in captivity without a permit. (It is, however, illegal to move the lizards out of the city areas where they are already found or to introduce them elsewhere in Ohio.) In town, there are now additional breeding groups in neighborhoods at Mount Adams, Over the Rhine, and the Cincinnati Zoo, and the scaley little fellows also apparently floated across the Ohio River (or perhaps were carried across by someone) and have become established in Newport, Covington, Park Hills, and Ft Thomas in Kentucky.
Others, however, have not been so accommodating to the invaders. When a group of Lazarus Lizards was found in Indiana along the banks of the Ohio River some 120 miles downstream, the response was swift and lethal. After genetic testing concluded that Indiana’s lizards had indeed come from Ohio (they apparently drifted downriver on a log or vegetation mat), Indiana undertook a successful program to hunt down every lizard and kill it.