Stunt Ranch Santa Monica Mountains Reserve

02 May, 02 AM - 07 May, 10 AM

The Role of Alternative Mating Strategies in Speciation Ammon Corl (PhD Candidate) 2007 Abstract of Proposed Research Sexual selection can be a powerful diversifying force leading to divergence within and among species. My aim is to extend microevolutionary studies of sexual selection to study speciation and macroevolutionary patterns of diversification. I am doing this by studying the geographic variation of the alternative mating strategies side-blotched lizard, Uta stansburiana. One hypothesis that I am testing is that changes in the number of alternative mating strategies can lead to accelerated morphological evolution. I am testing this by comparing phenotypic traits (such as sexual dimorphism and clutch size) between independent pairs of populations that have lost mating strategies vs. populations that have maintained mating strategies. Research at Stunt Ranch would provide such a comparison by allowing me to compare the phenotypes of lizards on Anacapa Island (with two mating types) to a mainland population of lizards at Stunt Ranch (with three mating types). In this way, I hope to link changes in mating strategy to morphological evolution. Introduction Sexual selection can be a powerful diversifying force leading to divergence within and among species. Sexual selection arises from competition for mates, usually from either male-male competition or female choice (Darwin 1859, 1871). Competition for mates can lead to a diversity of forms in different populations, extreme and exaggerated phenotypes within a species, and may accelerate rates of speciation (Darwin 1871; West-Eberhard 1983, Masta & Maddison 2002). Despite the role of sexual selection in shaping premating isolating mechanisms such as courtship behavior and species-specific signals, its role as a mechanism of speciation has been understudied (West-Eberhard 1983). Specifically lacking are studies that link microevolutionary processes of sexual selection within populations to macroevolutionary patterns of diversity (Panhuis et al, 2001). My research focuses on: 1. Investigating the geographic variation in the sexual signals (coloration) and morphology of the side-blotched lizard (Uta stansburiana) in order understand how sexual selection drives diversification within a species. 2. Studying replicated patterns of evolution among populations to study how sexual selection promotes large changes in phenotype. Investigating replicated patterns of evolution provides the statistical power to understand the forces that drive evolution. My aim is to extend microevolutionary studies of sexual selection to study speciation and macroevolutionary patterns of diversification. Study System One of the most comprehensive microevolutionary studies of mating systems and sexual selection is on the side-blotched lizard, Uta stansburiana. Within a population at Los Ba?os, CA three genetically determined male mating strategies engage in male-male competition. Males with orange throats are aggressive and control large territories with many females. Blue-throated males are less aggressive, closely guard females, and cooperatively defend territory (Sinervo & Clobert 2003). Yellow-throated males mimic female behavior and sneak on to other males? territories to copulate with females (Zamudio & Sinervo 2000). The fitness of each of these behavioral ?morphs? is dependent upon the frequency of the other types of males within the population. Thus, orange males are the most fit when blue is common, yellow is the most fit when orange is common, and blue is the most fit when yellow is common. This is just like a game of rock-paper-scissors and all three types of males are maintained in the population because no one male morph is able to win in every situation (Sinervo & Lively 1996). Within the same population there are also two different types of females. Orange-throated females (r strategists) are favored at low densities, for they produce large numbers of smaller progeny. Yellow-throated females (K strategists) are favored at higher densities, for they produce fewer, but higher quality offspring. Population density of adult females oscillates with a two year period which leads to the maintenance of both types of females (Sinervo et al., 2000). I have discovered significant geographic variation in the number of morphs of U. stansburiana (Corl, unpublished data). Mating types have been lost in multiple populations and in multiple subspecies of U. stansburiana. I have reconstructed a phylogeny of my study populations, which shows that there have been eight independent losses of mating strategies. The independent losses of mating strategies provide the replicate evolutionary events needed to test hypotheses about how the evolution of mating strategies affects phenotypic evolution. For example, preliminary analyses indicate that morph loss appears to be associated with divergence in sexual dimorphism. In this way, I am working to demonstrate that the loss of morphs is associated with accelerated phenotypic divergence. Focus of Proposed Research At Stunt Ranch In 2002, I visited Stunt Ranch and gathered data on the mating strategies found at Stunt Ranch. I found that Stunt Ranch had all three of the throat colors that characterize the rock-paper-scissors mating strategies. In addition, my genetic work has shown that the side-blotched lizards on Anacapa Island (of the Channel Islands) are closely related to the lizards found at Stunt Ranch. My colleagues and I have been studying the Anacapa lizards for ~7 years now and have discovered that they are quite different in a number of their characteristics. For instance, they have a reduced number of mating strategies (only orange and blue), they live much longer than lizards on the mainland, and they are larger in body size. I am hoping to further quantify the differences of the island lizards by comparing them to a population of close relatives on the mainland. This will provide a vital comparison between a population of lizards with three mating strategies to a population with only two mating strategies. This comparison will thus serve to quantify the phenotypic changes that occur when there is a change in the mating system. The lizards at or near Stunt Ranch seem like an ideal mainland population to study because they are closely related to the island lizards. I am hoping to return to Stunt Ranch to 1. gather more detailed morphological measurements of the lizards and 2. bring a few female lizards into the lab to lay their eggs so that I can get an estimate of the typical clutch size of the lizards. Data on clutch size will be particularly useful because while I have data on clutch size from many populations across the range of U. stansburiana, there is currently no data on the typical clutch size for lizards in the area of Stunt Ranch. Thus, I have no clutch size data to which I can compare the clutch size of the Anacapa lizards. Clutch size differences characterize the female throat color morphs in three morph populations and are thus an integral reproductive character to consider when studying the evolution of the alternative mating strategies. Data from Stunt Ranch would thus provide an important comparison between the clutch size of a three morph mainland population to a two morph island population. Methods At Stunt Ranch I propose to catch up to sixty lizards of each sex. This number of lizards will be sufficient to gather data on all the mating types of both the male and female morphs. The lizards are caught by a noose tied to the end of a fishing pole. The noose restrains the lizard, but does not physically harm them. Each lizard will be weighed, measured, and have its picture taken to record its coloration. The morphological measurements that will be taken are snout-vent length, mass, head length, head depth, head width, gape width, tail length, blotch height, and blotch length. The very tip of the tail (which can regenerate) is taken to provide tissue for DNA sequence analysis. Taking tail tips is a common herpetological practice and does negligible harm to the lizards. (All protocols have been approved by the Chancellor?s Animal Research Committee at UCSC.) Before being released the lizards will be marked with a dot of paint (which wears off after a week) to ensure that the same lizard is not caught again. Lizards are released at the point of capture typically within 24 hours. Of the lizards that are caught, 10-20 female lizards will be taken back to the Sinervo lab at the University of California at Santa Cruz to gather data on clutch size. Only females gravid with eggs (which can be assessed by abdominal palpitation) will be taken to lab. In the lab the females will be individually housed in a terrarium, fed with crickets, and provided with a heat lamp. When the females are ready to lay their eggs, they burrow into the peat moss in their terrarium and then lay their eggs. Clutch size and clutch mass can then be measured. Except by special permission, the Department of California Fish and Game requires that animals brought into the lab should not be returned to the wild. This is to prevent any possibility of disease introduction into the wild populations. Thus, the female lizards brought into the lab would be euthanized after laying their eggs. Removal of 10-20 female U. stansburiana will have a minimal impact upon the wild populations. Uta stansburiana are probably the most common lizard in California and 60-100 females can be found on just one hillside in some locations. This work is covered under the scientific collecting permit (SC#003574) of my advisor, Barry Sinervo. At this time I do not think any housing resources will be needed. However, I would be interested in knowing if overnight camping is allowed at Stunt Ranch. Sampling would take place from approximately 8 in the morning until 6 or 7 in the evening. Note that the dates I gave on my application are tentative right now. I am currently coordinating when I will be in southern California and able to sample lizards. Qualifications/Personnel Ammon Corl (Ph.D. candidate at the University of California at Santa Cruz) has been working for the past 5 years on the geographic variation and evolution of U. stansburiana. He has sampled side-blotched lizards across eight states, Mexico, and in multiple parks using the methods described above. His advisor is Dr. Barry Sinervo (Professor at University of California at Santa Cruz) who has been studying the behavioral ecology and evolution of U. stansburiana for the last 15 years. Dr. Sinervo has trained Ammon Corl in the methods described in this study.

Visit #12348 @Stunt Ranch Santa Monica Mountains Reserve

Approved

Under Project # 8133 | Research

The Role of Alternative Mating Strategies in Speciation

graduate_student - University of California, Santa Cruz

Reservation Members(s)

Group of 2 Graduate Student May 2 - 7, 2007 (6 days)
Ammon Corl May 2 - 7, 2007 (6 days)

Reserve Resources(s) | Create Invoice

Day Use Only 3 May 2 - 7, 2007