Current Research
Disruptive selection on color pattern in lizards In the Mojave Desert of California are several ancient lava flows that provide an opportunity to study disruptive selection in progress. We are working on two of these areas: 1) Cinder Cone National Natural Landmark in the Mojave National Preserve near Baker, CA and 2) Pisgah Volcano southeast of Barstow, CA. The main difference between the areas is that Cinder Cone is much older (7 million years old) than Pisgah (< 100,000 years old). Both areas are inactive lava flows of black and dark red basaltic rock, while the surrounding areas are composed of much lighter sand and granitic rocks. Lizards that are found on the dark lava have much darker dorsal coloration than lizards found on the lighter substrate. This color differentiation is highly likely to be under strong disruptive selection, because lizards of intermediate color do not match either substrate very well, and are more susceptible to predation. Genetic studies by graduate student Steven Micheletti has shown that light and dark side-blotched lizards (Uta stansburiana) from the Cinder Cone location are a single population with a bimodal distribution of color pattern, as one would expect if this were a case of disruptive selection. He showed that one of several candidate genes (melanocortin receptor 1) known to affect color variation in other lizard species does not seem to be correlated with color pattern differences in our population. One of our most interesting findings was that this population of lizards is extremely diverse, with haplotype diversities comparable to those found in marine fish sampled from throughout the world's oceans! We are continuing our investigations into the genetic architecture of color in Uta, and sampling other lizard species to compare them to the Uta results.
The above pictures are of 1) the sideblotched lizard (Uta Stansburiana) and 2) aerial view of lava field where collections were made. All photos were donated by Steven Micheletti.
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Genetics of speciation in Linanthus dichotomus (with Dr. Gretchen Lebuhn)
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