Dear Readers, living in the city is always a bit of a challenge if you’re used to the country – all those wide open spaces, all that concrete, all that fast food and the ever-present danger of getting squished by a bus (and that’s just for us humans). Imagine, then, the difficulties that a city environment presents to these little chaps – this Puerto Rico crested anole lizard (Anolis cristatellus) is normally found in the forests of Puerto Rico and the Virgin Islands, but has set up home on many other Caribbean islands. Increasingly, the lizards are moving into towns and cities, and scientist Kristin Winchell and her colleagues wanted to investigate how these urban animals differed from their country cousins.
First up, Winchell’s team discovered that city lizards had longer legs, presumably to enable them to navigate the pavements and squares at speed without being trodden on or picked off by predators. Secondly, those famously sticky toe pads were larger and stickier than usual, probably to enable them to climb glass and other shiny surfaces in search of their insect prey.
Winchell did some genetic analysis of city lizards from three different cities, and discovered that all of them had changes in the genes that controlled leg and skin development – this is a fine example of parallel evolution, where unrelated animals change in similar ways because the environment provides similar challenges. She also discovered that there were changes in a group of genes that affect immune function and metabolism – lizards in cities may be eating a non-optimal diet, and may also be subject to injuries that wouldn’t befall them in a forest, so a robust immune system would be a clear advantage.
However, the group of genes that have mutated to allow the lizard’s legs to grow longer, and their feet to grow stickier can also cause limb deformities in humans – it’s interesting to consider how many lizards ended up unable to function, and also what the knock-on effect might be on their offspring. In evolution there are always trade-offs, especially on the way to the best solution for a species. Plus, things never stand still – what works in one environment might have to be fine-tuned to work in another.
Incidentally, for a short while I had a pet anole – a different species to this one, with a pink crest under his throat. He mostly lived a very quiet life, but on one occasion I saw him flicking the little flag under his chin at an uncomprehending skink. I was entranced, but I quickly realised that keeping these little creatures in captivity for my own amusement was depriving them of most of the things that they needed to thrive – a mate and a rich and complex environment. How much better to observe wild creatures in their native habitat!
You can read the whole article here.