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Genetic, physiological, and ecological consequences of sexual and kleptogenetic reproduction in salamanders

Denton, Robert Daniel, Denton
http://rave.ohiolink.edu/etdc/view?acc_num=osu1501068314906519

Abstract Details

2017, Doctor of Philosophy, Ohio State University, Evolution, Ecology and Organismal Biology.
Every year, there is at least one widespread news story documenting a “virgin birth” in a variety of animals as diverse as snakes and sharks. These events capture our attention because they represent departures from an assumed necessity of vertebrate life: having sex. Yet, vertebrates do not always reproduce via sex, and biologists have long studied the evolutionary costs and benefits of this type of reproduction. One of the main costs of sex are males, who cannot directly generate offspring and use up resources from reproductive females that cannot be put towards additional offspring. Eastern North America is home to one of the strangest vertebrates that lack males and appear to be sexual and asexual at the same time: an all-female group of salamanders that appear to “steal” sperm from males of other species. These all-female salamanders can potentially retain the advantage of gaining new genetic diversity from other species without males of their own. However, the extent and flexibility of this mating systems is still not understood, and the factors that promote the coexistence of all-female salamander lineages and the sexual species from which they use reproductive material are mysterious. I have investigated three primary questions concerning these unusual animals. First, how do we identify an all-female salamander in Ohio? Because of their cryptic morphology compared to similar sexual species, all-female Ambystoma salamanders are only reliably identified by sequencing their mitochondrial DNA, which is independently transferred maternally. However, mitochondrial sequences that closely resembled those of all-female salamanders were previously found in salamander individuals across Ohio that were identified morphologically as either the smallmouthed or streamside salamander. I gathered microsatellite data from these potentially misidentified animals and evaluated three hypotheses for why the mitochondrial data does not match the nuclear DNA or morphological species identity. The best supported hypothesis was one of mitochondrial introgression, where the mitochondrial haplotypes of one species (streamside salamanders) were introgressed into populations of another species (smallmouth salamanders). This chapter describes the evolutionary basis for the discordance between mitochondrial and nuclear DNA markers and provides necessary diagnostic information to correctly identify all-female salamander lineages in Ohio. Second, can differences in dispersal between breeding environments dictate the coexistence between all-female salamanders and other salamander species, preventing mutual extinction? I inferred salamander movements across a fragmented agricultural landscape in Ohio with genetic data and treadmill endurance trials, and I found that sexual species traveled significantly greater distances between breeding sites and fatigue much more slowly than unisexuals, contrary to a hypothesis that would explain the ecological coexistence between these groups. Third, what environmental factors determine the coexistence of all-female salamanders and their sexual relatives at broad scales? I gathered rangewide occurrence data for blue-spotted, Jefferson’s salamanders, and all-female salamanders that vary by the number of nuclear genomes possessed from either sexual species. By comparing the niche overlap from ecological niche models representing all-female salamander groups and each sexual species, I found that neither the total number of genomes or the composition of all-female salamander genomes explained the amount of niche overlap. Instead, niche overlap was significantly greater than expected for all comparisons between sexual species and the all-female lineage. I additionally used joint species modeling techniques to suggest that species interactions, in this case the all-female salamanders’ reproductive requirement for sperm, are the most powerful predictor of ecological niche in all-female salamanders and limit their ability to differentiate from their sexual relatives. Taken together, these chapters have expanded our understanding of how all-female salamanders have evolved to navigate the tradeoffs of intermediacy between sexual and asexual reproduction while providing new avenues of research for the future, including physiological limitations in members of the all-female lineage and molecular discordance between their separate mitochondrial and nuclear genomes.
H. Lisle Gibbs (Advisor)
Bryan Carstens (Committee Member)
Peterman William (Committee Member)
135 p.
Biology; Ecology; Evolution and Development; Organismal Biology
asexual reproduction; kleptogenesis; salamanders; Ambystoma; Dispersal; Niche Modelling; Introgression

Recommended Citations

Citations

  • Denton, Denton, R. D. (2017). Genetic, physiological, and ecological consequences of sexual and kleptogenetic reproduction in salamanders [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1501068314906519

    APA Style (7th edition)

  • Denton, Denton, Robert. Genetic, physiological, and ecological consequences of sexual and kleptogenetic reproduction in salamanders. 2017. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1501068314906519.

    MLA Style (8th edition)

  • Denton, Denton, Robert. "Genetic, physiological, and ecological consequences of sexual and kleptogenetic reproduction in salamanders." Doctoral dissertation, Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1501068314906519

    Chicago Manual of Style (17th edition)

osu1501068314906519
340
© 2017, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.