Polymorphism and male competition are both well-documented and well-studied phenomena in nature, but rarely have they come together in such a unique way. The common side-blotched lizard (Uta stansburiana) is a polymorphic species where competition between three male morphs can be likened to a game of rock, paper, and scissors. This GEM will explore the evolution of the rock-paper-scissors dynamic found in male side-blotched lizards and the selective forces that maintain it.
The three discrete male morphs differ in the coloring of their throat and the reproductive strategy that they use. Orange-throated morphs are the most aggressive, controlling the most territory and subsequently, the largest number of females. Blue-throated morphs are less…show more content… Orange-throated morphs have the highest levels of T and the highest levels of aggression and endurance, two traits needed to successfully maintain a large territory and defend a large group of females. Blue morphs have intermediate levels of T and endurance, and yellow have the lowest. Corl theorized that the ground morphological state of the lizard resembles that of yellow-throated females and that changes in levels of T gave rise to different male morphs.
The alternative mating strategies of the three morphs display a rock-paper-scissors dynamic. Orange-throated morphs can easily over take blue territory. Yellow-throated morphs can easily sneak into orange territory. Blue-throated morphs can easily guard against yellow invasion. Sinervo and Lively tracked morph frequencies in a population over a 5-year period and found that the dominant morph in a population shifted from blue, to orange, to yellow, and back to blue morphs, in a cyclic…show more content… Because male morphs are consistently most fit, and give the most number of successful offspring, when they are rare, both types of females will mate with the most rare male morph. Success of future female offspring depends on future female morph frequencies. In high-density years, females will mate with orange males to produce orange daughters for the following low-density year. In low-density years, females will mate with blue or yellow males to produce yellow daughters for the following high-density year. Because female and male morph cycles do not always match up, and the best mate choice for the most successful male offspring may conflict with the best mate choice for the most successful female offspring, female choice often results in a trade off between fit sons and fit daughters. Female mate choice can accelerate or slow the male morph cycle, depending on whether or not they select the rare male
