Specimen Spotlight -- Side-blotched Lizard
The Side-bloched Lizard (Uta stansburiana) has different male mating strategies characterized by distinct throat colors and mating behaviors. We can compare their mating strategies to the rock-paper-scissors game: orange males take territory from blue males because they are more aggressive, yellow males beat orange males by sneaking onto their large territories, and blue males beat yellow males by closely guarding their mates. Selection therefore maintains all of the mating types in the population because the fitness of a particular type depends on which other type it is competing against. When such distinct differences among individuals occur within a single population of a species, scientists call this a polymorphism.
Ammon Corl, a current MVZ Post-Doc, studied the geographic variation and evolutionary history of this mating strategy polymorphism for his Ph.D. thesis. He discovered that the side-blotched lizard mating strategy polymorphism is geographically widespread across the western U.S. and is the likely ancestral state for the species. These results demonstrated that rock-paper-scissors dynamics can maintain a polymorphism for millions of years. However, it appears that even this highly stable system for maintaining diversity can destabilize, as there have been eight independent losses of the polymorphism. Widespread convergent evolution has occurred because in all cases the allele that gives rise to the yellow sneaker male strategy has been lost (e.g. the two lizards pictured above come from Anacapa Island, which only has orange and blue morphs). There are also populations fixed on a single color type (e.g. the orange lizard below).
The MVZ houses 4244 Uta stansburiana specimens in its collections, collected between 1899 and 2005. This species represents one of the most abundant and commonly observed lizards in deserts of Western North America, which likely explains why the museum has so many. That said, the MVZ has become well-known for its habit of collecting many specimens from a single location. This allows scientists who use the collections to answer complex ecological and evolutionary questions that would not be possible when comparing the characteristics (genetic, morphological, geographic, etc.) of only a few specimens.
The colors that characterize side-blotched lizard morphs appear in the spring breeding season and then fade away during the rest of the year. The colors also will fade away in preserved museum specimens (as shown in the photographs above and below), which presents a problem for many other species of reptile as well. This highlights a need for researchers to take photographs of animals in the field to accompany preserved specimens, so that the true appearance of a individual in life can be known and used for research purposes. This has now become common practice at many collecting institutions, including the MVZ.
—Written by Ammon Corl