Much of the work I’m doing for my Masters focuses on rates of molecular evolution in plants, specifically neutral; molecular evolution, that is, areas of the genome that are not under any strong selection and are ‘free’ to gather mutations without constraint.
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I’m specifically looking at the effect of environmental conditions on those rates, and without giving too much away, rainfall.
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Anyway, a recent article by some New Zealand researchers, including Dr. Craig Millar from my department at the Univeristy of Auckland, presents some very interesting data within the field that I’m working in, and it’s seriously cool…
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Tuataras are ancient animals, in that they are the only living representative of a lineage of reptiles (the Sphenodontia) that emerged early during the age of the dinosaurs, some 220 million years ago. Since then, they have undergone very little morphological evolution, hence their designation as a ‘living fossil’. They are poikilothermic (cold blooded), they have very low metabolic rates, they grow very slowly, and they reproduce even slower. As a result, and in line with their minimal morphological change, it could be expected that they have a relatively low rate of neutral molecular evolution.
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Well, apparently not. Using ancient and modern Tuatara bones, the authors were able to show that the rate of tuatara mitochondrial DNA change isn’t even similar to warm blooded, rapidly breeding animals which have changed their appearance and body structures relatively rapidly over time, but much much faster. Amazing!
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This has two important consequences. Firstly, it shows that rates of change to DNA aren’t necessarily matched by rates in morphology or appearance – an animal like the tuatara has changed very little in appearance over the last 220 million years, compared to say a Moa, or a Horse or Cave Lion, which have, relatively speaking, changed very rapidly in the intervening years. Moreover, and more importantly for me: the rate of molecular evolution isn’t necessarily bound to environmental conditions such as temperature, or to life history characteristics like generation time, or even endogenous factors such as metabolic rate.
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This field just gets more and more interesting every day! O.o
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Article:
Rapid Molecular Evolution in a living fossil
Jennifer M. Hay, Sankar Subramanian, Craig D. Millar, Elmira Mohandesan and David M. Lambert
Trends in Genetics 24(3):106-109
Recent Peer Review