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Mark Jordan; Scott Bergeson




The Ambystoma Unisexual (unisexual mole salamander) is an all-female salamander species that reproduces asexually. Their existence and persistence has been a conundrum for biologists, since the advantages of the unisexual reproduction must be weighed against the expected fitness advantages (i.e., genetic variation) that are generally characteristic of sexual reproduction. Kleptogenesis is a reproductive mode that has been proposed for this species of Ambystoma. Particularly, unisexual Ambystoma can attract and mate with bisexual males. After acquiring sperm from a bisexual male, unisexual Ambystoma’s eggs will pass through one of the following scenarios. First, the egg might be stimulated to develop without incorporating the sperm. Second, the egg might incorporate the sperm and one (or two) of the egg’s set of chromosome is replaced by the sperm’s. Finally, the egg could incorporate the sperm and add one of the sperm’s sets of chromosome into its genome, elevating its ploidy level. Due to these various scenarios, the unisexual Ambystoma is diverse in genomic pattern.The genome variation for a particular unisexual individual is labeled according to the initials of the species of the sperm donors contributing to its genome. For example, a unisexual that has one genome from A. laterale (L), one from A. jeffersonianum (J), and two from A. texanum (T) will be labeled as LTTJ. A population consisting of unisexual Ambystoma and A.texanum (small-mouthed salamander) is found at the Eagle Marsh Natural Preserve, Allen County. The genomic pattern in the population suggests that Ambystoma texanum had, at one point in its history, contributed its genome to the unisexual’s gene pool, elevating LJ to LTJ, and sometime later on, contributed again, elevating LTJ to LTTJ. However, it is unknown whether A. texanum is still mating with and contributing genetic information to the unisexual Ambystoma’s (both LTJ and LTTJ) gene pool or not. The goal of this research is to answer that question. Specifically, we are trying to find out if A.texanum is still actively replacing existing T genome in the unisexuals or the contributions that led to ploidy elevation or ploidy alternation in the unisexual are the only genetic contributions in its history. If the latter occurred, then the subsequent asexual reproduction in unisexual Ambystoma must have given rise to other unisexual that are identical to their parents in the population. I hypothesize that A. texanum is no longer contributing to the unisexual population’s gene pool and, thus, has only genetically contributed to the population twice in its history. To test this hypothesis, I will collect A. texanum samples during the next few springs. I will then use microsatellite Atex74, which is unique to A. texanum and is also found in unisexual Ambystoma (both LTTJ and LTJ). Atex74 will undergo the PCR process and electrophoresis for allelic similarities to determine the relationship between A.texanum and unisexual Ambystoma located at Eagle Marsh.



The Genetic Contribution of Small-mouthed Salamanders to Unisexual Salamander's Genome

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