Still Just a Lizard
Posted on June 4, 2008 Comments (1)
Still just a lizard by PZ Myers
The original population of P. sicula was still present on Pod Kopiste, so we have a nice control population. These lizards are small, fast, insect-eaters in which the males defend territories. Sadly, P. melisellensis on Pod Mrcaru had been extirpated. So we had a few innocent casualties of the experiment.
The transplanted P. sicula thrived and swarmed over the island of Pod Mrcaru, but they were different, and they had evolved in multiple ways.
The original P. sicula were insectivores who occasionally munched on a leaf; approximately 4-7% of their diet was vegetation. The P. sicula of Pod Mrcaru, though, had adopted a more vegetarian diet: examining their gut contents revealed that 34% of their diet was plants in the spring, climbing to 61% in the summer…and much of this diet was hard-to-digest stuff, high in cellulose. This is a fairly radical shift.
There were concomitant changes. The lizards’ skulls were wider, deeper, and longer, and they had stronger bites — a necessity for chomping off bits of tough plants, instead of soft mosquitos. Instead of chasing bugs, they’re browsing stationary plants, and their legs are shorter and they are slower. Population densities are higher. The Pod Mrcaru lizards no longer seem to defend territories, so there have been behavioral changes.
Still just a lizard, I know.
Now here’s something really cool, though: these lizards have evolved cecal valves. What those are are muscular ridges in the gut that allow the animal to close off sections of the tube to slow the progress of food through them, and to act as fermentation chambers where plant material can be broken down by commensal organisms like bacteria and nematodes — and the guts of Pod Mrcaru P. sicula are swarming with nematodes not found in the guts of their Pod Kopiste cousins.
Related: Evolution is Fundamental to Science – Evolution at Work with the Blue Moon Butterfly – Two Butterfly Species Evolved Into Third – Gecko Tape
Categories: Life Science, Research, Science, Students
Tags: animals, evolution, scientific inquiry
One Response to “Still Just a Lizard”
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June 5th, 2008 @ 11:43 am
interesting story!good post!i think you are a scientist or expert of science,
because your posts coverred a lot of information about theme of science, my
major in college is biology, so i feel your post friendly to me.