Evolutionary and Conservation Genetics of Reptiles

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Closely related females of wild species of animals are often found side-by-side rather than being broadly mixed with more distantly related females of the same species. A narrow geographic break separates females of more distant lineages. The region where both lineages occur may be only 6km or less. Curiously, on the narrow peninsula of Baja California, Mexico, most species of animals show a pattern of neighbouring lineages in the middle of the peninsula. These have lived side-by-side for more than 3 million years without mixing and in some cases for much longer periods of time. A key focus of my research is to determine why this common pattern is so universal among animals. In other words, why do females not disperse more than 6km given more than 3 million years to do so? After all, this distance amounts to only 2mm/year! One explanation, termed cytonuclear discordance, suggests that the lineages do not mix because their energy-producing enzymes do not work efficiently when they are mixed. By analogy, this phenomenon is like trying to put a square peg of one lineage into a round hole of another. Another possibility is that females protect their families against intruders, and this novel explanation, which is analogous to battle-lines, I call the sisterhood hypothesis. To make the situation complex, both of these explanations may work together in concert to maintain the pattern. I will use a suite of experiments with tree lizards to evaluate cytonuclear discordance, the sisterhood hypothesis, and the relative roles played by each of these mechanisms in maintaining the pattern of side-by-side maternal lineages. The experiments range from determining the relatedness of females on a given tree, be they mother-daughter, sisters, cousins, or more distantly related, and sophisticated models of protein structure to evaluate how the enzymes work together. The analyses have implications for not only understanding how species evolve, but also for conservation and management initiatives, especially as they relate to species translocations.