Mate choice and competition in the eastern fence lizard, Sceloporus undulatus
Open Access
- Author:
- Swierk, Lindsey Noele
- Graduate Program:
- Ecology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 21, 2013
- Committee Members:
- Tracy Lee Langkilde, Dissertation Advisor/Co-Advisor
Victoria Braithwaite, Committee Member
David Peter Hughes, Committee Member
James Landis Rosenberger, Special Member - Keywords:
- behavior
competition
courtship
eastern fence lizard
mating
reproduction
Sceloporus undulatus - Abstract:
- Sexual selection exerts a strong influence on the evolution of phenotypes across taxa. In animals, sexual selection is largely driven by competitive social interactions among individuals of the same sex (often male) for access to the opposite sex (female). Because some traits, such as weaponry or courtship behavior, enhance an individual’s ability to outcompete rivals and attract mates, elaborate phenotypic traits are often selected via mate competition. My dissertation addresses the underlying processes of trait evolution via sexual selection by examining how phenotype affects the outcome of intra- and inter-sexual mating competition. Here, I present results from inter- and intra-sexual competition studies of eastern fence lizards (Sceloporus undulatus)— a polygamous, territorial species that uses a suite of phenotypic signals and cues in mating competition. Notably, fence lizards perform dramatic physical displays when courting and defending resources, and males bear vibrant blue throat and abdominal badges used in sexual signaling. I examined if female fence lizards used multiple cues and signals (behavioral and morphological) when selecting mates, and found that females not only assess multiple traits, but also weight some male traits more heavily than others in their decision-making. Territory quality is known to have a role in female decision-making, but is rarely controlled when assessing female choice of mates. My results reveal that female choice may directly influence the evolution of male traits, rather than only indirectly selecting for male traits implicated in territory maintenance. I next examined the determinants of male behavior in male-male contests for mate access, to identify how a male’s phenotype, his competitor’s phenotype, and the value of the contested resource (female quality) influenced male competitive tactics. I found that male fence lizards observe rival behavior and respond with finely-tuned signals based on their own quality relative to that of their rival. I also examined whether males exerted mate choice on female traits, by allowing males to choose between two females and found that males discriminate between mates based not only on female body condition, but also on female behavior: males preferred females that performed receptive sexual behaviors. Finally, I tested whether sexual conflict was evident in the production of blue ventral badges in fence lizards – some females bear rudimentary badges that appear to be merely a byproduct of strong selection for badges in males. My results provide evidence of a tug-of-war in optimal phenotype: males benefited from badges, but rudimentary male-typical badges in females correlated with lower reproductive output and male rejection of females as mates. Together, the results of my dissertation research highlight the role of morphology and behavior on individual fitness via their effects on the outcome of mating competition, and expand our understanding of the processes by which social interactions shape the evolution of phenotypes.