ORCID Identifier(s)

0000-0002-3807-1395

Graduation Semester and Year

2016

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Quantitative Biology

Department

Biology

First Advisor

Matthew K Fujita

Abstract

Clonal lineages are expected to experience a decline in fitness over time due to their inability to decouple deleterious and beneficial alleles. Individually, however, asexual populations pass twice as much of their DNA per generation as sexual lineages. This balancing act between Muller's Ratchet and the lack of the two-fold cost of sex in asexuals brings significant scientific intrigue to instances of asexual populations. Among vertebrates, squamates (and mainly lizards) are uniquely capable of true parthenogenesis whereby females reproduce without males. These lineages are always hybrid, as is the case with parthenogenetic Aspidoscelis lizards (Teiidae). In particular, the checkered whiptail lizard A. tesselata exhibits phenotypic diversity in color and scalation. This could be caused by multiple hybrid origins, genetic input from other clades (hybridization or lateral gene transfer), gene conversion, epigenetics, or mutation. De novo mutations are generally called upon as the main source of variation in clonal parthenoforms, but this hypothesis remains largely untested A. tesselata. Here, we investigate three topics pertaining to diversity in clonal A. tesselata and other whiptails: 1) A. tesselata may have arisen by multiple hybrid origin events; 2) A. dixoni, a close relative of A. tesselata, is a post-formational lineage derived from A. tesselata, with a description of a new population from northern Texas; and 3) using a newly sequenced and facultatively parthenogenetic Aspidoscelis genome, homogeneous regions of the genome (i.e., isochores) in Aspidoscelis are intermediate in diversity between genomes with high and low isochore diversity. Using ddRADseq, mitochondrial genomes, and ecological niche modeling, we found A. tesselata originated from limited origins – estimated one or two – and that this occurred 134.3–588.2 thousand years before present (95% HPD). Additionally, diploid A. tesselata are paraphyletic without including A. dixoni. Finally, we recover a spread of genomic heterogeneity across four groups of vertebrates and found intermediate isochoric diversity within Aspidoscelis compared to the Anolis carolinensis and Homo sapiens genomes.

Keywords

Aspidoscelis, Whiptail, Parthenogenesis, Evolution, Population genetics, Phylogenetics, Isochore, Genome, RADseq, ENM, Niche model, Reptile, Lizard, Teiidae, Aspidoscelis tesselata, Aspidoscelis marmorata, Aspidoscelis gularis, Aspidoscelis dixoni

Disciplines

Biology | Life Sciences

Comments

Degree granted by The University of Texas at Arlington

Included in

Biology Commons

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