Symposium: The Biology of Whiptail Lizards IIRoom: Room 206C2022-07-31 13:30 - 15:00 |
| Moderator: Robert Thomson |
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1. 13:30 Mitochondrial Mutation Accumulation in Parthenogenetic Whiptail Lizards (Aspidoscelis). Jose Maldonado, The University of Texas at Arlington; TJ Firneno, University of Denver; Alexander Hall, Thermo Fisher Scientific; Matthew Fujita*, The University of Texas at Arlington mkfujita@gmail.com
Sexual reproduction is ubiquitous in the natural world, suggesting that sex must have extensive benefits to overcome the cost of males compared to asexual reproduction. One hypothesized advantage of sex with strong theoretical support is that sex plays a role in removing deleterious mutations from the genome. Theory predicts that transitions to asexuality should lead to the suppression of recombination and segregation and, in turn, weakened natural selection, allowing for the accumulation of slightly deleterious mutations. We tested this prediction by estimating the dN/dS ratios in asexual vertebrate lineages in the genus Aspidoscelis using whole mitochondrial genomes from seven asexual and five sexual species. We found higher dN/dS ratios in asexual Aspidoscelis species, indicating that asexual whiptails accumulate non-synonymous substitutions due to weaker purifying selection. Additionally, we estimated nucleotide diversity and found that asexuals harbor significantly less diversity. Thus, despite their recent origins, slightly deleterious mutations accumulated rapidly enough in asexual lineages to be detected. We provide empirical evidence to corroborate the connection between asexuality and increased amino acid substitutions in asexual vertebrate lineages. |
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2. 13:45 Species boundaries and pervasive gene flow in the spotted whiptail lizards (Aspidoscelis gularis complex). Anthony Barley*, University of California, Davis; Adrián Nieto Montes de Oca, Universidad Nacional Autónoma de México; Norma Manríquez-Morán, Universidad Autónoma del Estado de Hidalgo; Robert Thomson, University of Hawaii ajbarley@ucdavis.edu
Identifying the boundaries between species and resolving evolutionary history in the presence of gene flow is essential to understanding diversification processes in recent radiations. Here we approach this problem by focusing on the evolutionary process of species formation, integrating population genetic and phylogenetic tools to resolve the systematics of the spotted whiptail lizards of the genus Aspidoscelis (A. gularis complex). This complex of lizards is among the most important to understanding the numerous evolutionary transitions from sexual to unisexual reproduction that have occurred within Aspidoscelis, yet long standing confusion about their systematics has impeded understanding of which lineages have been important in this process. Using reduced representation genomic data, we resolve patterns of divergence and gene flow within the spotted whiptails, clarify which lineages have been involved in the formation of the unisexual lineages, and discuss the taxonomic implications of our results. We find that biogeographically structured ecological/environmental variation has been important in the diversification and maintenance of species boundaries in this system. Our study has implications for understanding diversification in rapid radiations and resolving long-standing taxonomic challenges in the field of systematic biology. |
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3. 14:00 A plague of lizards: parthenogenic whiptails are spreading throughout urban Southern California. Sam Fisher*, La Sierra University; Rich Inman, USGS; Todd Esque, USGS; Kathy Baumberger, USGS; Adam Backlin, USGS; Monique Wong, USGS; Greg Pauly, 3Department of Herpetology and Urban Nature Research Center, Natural History Museum of Los Angeles County sfis086@lasierra.edu
Invasive reptiles can have detrimental impacts to the areas where they invade. Within Southern California, the non-native Sonoran Spotted Whiptail (Aspidoscelis sonorae) has been rapidly spreading. They have been present within Orange County for at least ten years, and we recently determined they have been present within San Diego County for at least three years. For A. sonorae, we assessed habitat suitability, minimum amount of recent spread, and the potential for interspecies impacts. Community science observations have been useful in tracking the spread of A. sonorae, and we combined these with standardized walking and biking surveys across both counties to further assess spread. Additionally, we created diagnostic keys to differentiate the non-native whiptail from morphologically similar native species. We found that invasive A. sonorae have a high degree of habitat suitability across Southern California, with invasive populations currently residing in sub-optimal areas. Aspidocelis sonorae has spread over at least 83 square km in Orange County and 3 square km in San Diego County. There have been no measurable changes to urban lizard diversity in areas whereA. sonorae have spread, and there is no evidence yet that they are found in areas where they would be in direct competition with native whiptail species. Continued surveys are needed to track the spread of this invasive species. |
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4. 14:15 Discussion |