An integrative approach to the ecology and evolution of alternative reproductive tactics in male Poecilia latipinna




Kim, Son Young

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Understanding the sources of variation that make up complex phenotypes has been a long-standing goal of evolutionary biology. Sexually-selected polymorphisms such as those found in alternative reproductive tactics (ARTs) are an example of complex phenotypes that show extreme variation among multiple traits. Males often show phenotypic traits that vary in size, ornamentation, coloration, and behavior. For my dissertation, I used an integrative approach to investigate aspects of the social, hormonal and genetic effects that contribute to alternative reproductive tactics using male sailfin mollies, Poecilia latipinna, a live-bearing fish species. Complex phenotypes have both genetic and environmental sources of variation, and hormones often mediate the interaction between these two sources. Maternal effects and the presence of rival males are two such social environmental factors that can affect male phenotypes. First, I examined the effects of other rival males on male mate choice for conspecific females, and on the changes in circulating levels of the androgen 11-ketotestosterone (KT) and cortisol within a mate choice context. Although rival males did not affect male mate choice, these potential competitors did affect the KT release rates of focal males and females. Further, males released more KT with increasing size of the rival male. Then, I investigated how cortisol release rates varied in female sailfin mollies during gestation to identify the potential effects of maternal stress on son phenotype. I conducted an adrenocorticotropic hormone (ACTH)-challenge to determine the natural range of cortisol by gestating and non-gestating females and whether within and among individual variation (repeatability) contributed to female cortisol release rates. Gestational status did not correlate with cortisol but females showed high repeatability in cortisol release rates which suggests that variation in maternal stress may affect offspring and that cortisol release rates may be heritable. Lastly, I identified the genetic basis of male phenotypic variation using a genome-wide association study. Using a Bayesian sparse linear mixed model approach, I characterize the underlying genomic architecture of relevant morphological traits that define ARTs in male sailfin such as body size. I found that the phenotypic traits associated with ARTs in male sailfin mollies show a complex genetic architecture with many loci of small effect, which suggests that these ART traits are polygenic and reflect high heritability. Together, these chapters provide greater understanding of the genetic and physiological mechanisms for the variation in male phenotypes of sailfin mollies.



Allostasis, Androgens, Genotype-by-sequencing, Glucocorticoids, Gynogenetic, Heritability, Mate preference, Next-generation sequencing, Poeciliidae, Reactive scope


Kim, S. Y. (2019). <i>An integrative approach to the ecology and evolution of alternative reproductive tactics in male Poecilia latipinna</i> (Unpublished dissertation). Texas State University, San Marcos, Texas.


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