In the foothills around the Strathbogies, in grassland and grassy-woodland habitat occur lizards, legless-lizards, that look just like small snakes: the Olive Legless-lizard (Delma inornata) and the Striped Legless-lizard (D. impar). And they look like snakes, because they have evolved to lead a snake-like life-style; slithering through grass and squeezing into tight, narrow cracks in the ground and under rocks, where legs are a hindrance.
Evolution that results in organisms (that don’t have a close common ancestor) becoming more alike, like snakes and legless lizards, is called convergent evolution. In fact many groups of reptiles have independently evolved limblessness. Unfortunately for our legless-lizards, this often results in death at the hands of fearful, or unaware, human intervention.
Recently, I ‘discovered’ a more subtle, yet no less surprising example of convergent evolution relating to legless-lizards.
In my friend’s garden are several compost bins. To stop weeds growing he covers the vegetable matter in the bins with old carpet. He knows that I’m interested in legless-lizards and has been telling me for years that he has them in his garden. So, when I was finally in Tom’s garden about two weeks ago, he took me to the compost bins, lifted the carpet and, lo-and-behold, there they were. Clearly they were legless-lizards and almost indistinguishable from the Delma species we have in our region; Tom and the locals call them ‘Slow Worms’.
Only one problem – I was on a garden allotment in London, the one in England! Legless-lizards in England?? … they hardly even have snakes, so what was I looking at? They are, in fact Anguis fragilis a legless-lizard occuring though parts of Europe, Britain and Asia. They are not closely related to Australian legless-lizards and undoubtedly evolved their leglessness quite separatley, as a result of their ancestors inhabiting similar habitats to the ancestors of Delma. And like our legless-lizards, Slow Worms also drop their tails as a defence mechanism, as can be seen in this image. One slight difference between local legless-lizards and Slow Worms, is that the former have vestigial hind-limb flaps, but Slow Worms have completely lots all external sign of limbs.
So not only can lizards evolve to look like snakes, different groups of lizards in very different parts of the world have evolved similar strategies, limblessness, to adapt to local conditions and end up looking nearly identical.