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Intralocus Tactical Conflict as a Constraint on the Evolution of Alternative Reproductive Tactics in Xiphophorus multilineatus (Cyprinodontiformes: Poeciliidae)

Liotta, Melissa Nena
http://orcid.org/0000-0002-0302-0862
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1595958658568295

Abstract Details

2020, Doctor of Philosophy (PhD), Ohio University, Biological Sciences (Arts and Sciences).
Alternative reproductive tactics (ARTs) occur when members of the same sex within a species are dimorphic for reproductive phenotypes. ARTs typically evolve in response to strong sexual selection and involve alternate ways to gain reproductive success through suites of correlated behavioral, morphological, and life history traits. Due to their shared genome, ARTs likely share the genetic architecture for homologous traits, yet may have different phenotypic optima for these traits. If this is the case, the evolution of dimorphism or further dimorphism towards an ART’s specific optimum may be constrained by their genetic architecture, resulting in intralocus tactical conflict (IATC). Studies on the evolutionary effects of intralocus conflict have mainly focused on shared traits between the sexes, while investigations into intralocus conflict on ARTs is relatively new. My dissertation investigates whether IATC is acting on shared reproductive traits between the male ARTs of the swordtail fish Xiphophorus multilineatus. Xiphophorus multilineatus males exhibit two ARTs, a courter that uses only courtship to attract females, and a sneaker that is behaviorally plastic and uses both courtship and forced copulatory sneak-chases. In chapter 1, I characterized the dimorphism between courter and sneaker males for body shape, which has implications for swimming performance and thus successful execution of each ARTs’ mating behavior. In addition, I investigated the relationship between body shape and mating behavior in the sneaker males to determine if sneak-chase and courtship is phenotypically integrated with body shape. I found that courter and sneaker males are dimorphic for body shape, even when males overlap in size, and that more fusiform sneaker males are more likely to use sneak-chase behavior. In chapter 2, I used measures of reproductive success from a wild population to estimate selection gradients on three tactically dimorphic traits involved in sexual selection: body size, body shape, and sword length. This allowed me to investigate two of the three criteria necessary to demonstrate that IATC is acting on a trait: 1) that ARTs are not at their phenotypic optima for a trait and 2) that ARTs have different phenotypic optima for a trait. I found that body size and sword length meet the two criteria. I was able to detect a signal of selection acting on body shape for courter males, demonstrating that courters are not at their phenotypic optima for body shape, but not for sneaker males. No signal for selection on body shape for sneaker males suggests that the behavioral plasticity of this ART may be buffering the signal of selection. In chapter 3, I investigated the final criteria for IATC, that the ARTs are genetically correlated for shared traits of interest, by breeding a three generation half-sibling pedigree and using animal models to estimate additive variance. Although I was unable to recover genetic correlations for my four morphological traits of interest (standard length, body depth, sword length, and number of vertical bars), I did find that there is heritable variation present for these traits, and I demonstrated a method for exploring the response to selection between ARTs by using information from my selection analyses and the pedigree. In chapter 4, I again compared the relationship between body shape and mating behavior across experienced wild-caught sneaker males and inexperienced lab reared sneaker males to explore the role of behavioral plasticity in this ART and the possibility that the previous relationship found in chapter 1 is learned. I found that regardless of experience more fusiform sneakers are more likely to use sneak-chase behavior, suggesting that the phenotypic integration between morphology and behavior may not be learned but instead may be genetically integrated. These studies clearly demonstrate strong evidence for two of the criteria for IATC, that courters and sneakers have different phenotypic optima for shared traits and that that they are not at their respective optimum. This work was unable to demonstrate the third criterion; however, it has provided valuable methods for exploring IATC between ARTs and insights into the role of behavioral plasticity in IATC.
Molly Morris, PhD (Advisor)
160 p.
Biology
Intralocus Tactical Conflict; Genetic Conflict; Tactically Antagonistic Selection; Alternative Reproductive Tactics; Tactical Dimorphism; Behavioral Plasticity; Genetic Correlations; Heritability; Response to Selection; Xiphophorus multilineatus

Recommended Citations

Citations

  • Liotta, M. N. (2020). Intralocus Tactical Conflict as a Constraint on the Evolution of Alternative Reproductive Tactics in Xiphophorus multilineatus (Cyprinodontiformes: Poeciliidae) [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1595958658568295

    APA Style (7th edition)

  • Liotta, Melissa. Intralocus Tactical Conflict as a Constraint on the Evolution of Alternative Reproductive Tactics in Xiphophorus multilineatus (Cyprinodontiformes: Poeciliidae). 2020. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1595958658568295.

    MLA Style (8th edition)

  • Liotta, Melissa. "Intralocus Tactical Conflict as a Constraint on the Evolution of Alternative Reproductive Tactics in Xiphophorus multilineatus (Cyprinodontiformes: Poeciliidae)." Doctoral dissertation, Ohio University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1595958658568295

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Ohio University and OhioLINK.