Parthenogenetic lizards are the only naturally-occurring amniote systems that offer an opportunity to examine the evolutionary consequences of an asexual life history on entire genomes. In particular, parthenogenetic lizards are often associated with several genomic anomalies, including: (1) large, tandem duplications in their mitochondrial genomes, (2) hybrid origin, and (3) polyploidy.
Molecular evolution of mitochondrial genomes
Typical mitochondrial genomes have a conserved gene order and content, and in vertebrates are ~14-17 kb in size. Parthenogenetic lizards often have very large tandem duplications, often >10 kb in length, and these duplications include protein-coding, tRNA, and RNA genes, as well as the control region in some cases. Our lab uses whole mitochondrial genome sequencing to study the patterns and processes that generate these duplications and their subsequent evolution. For instance, in parthenogenetic Heteronotia, my colleagues and I found evidence for degenerative mutations, leading to mitochondrial pseudogenes. We are currently expanding our studied to additional taxa, including Aspidoscelis.
Dynamics of parthenogenetic genomes
The vast majority of parthenogenetic lizards had a hybrid origin, and of those a significant percentage are polyploid (typically triploid). The hybrid polyploid nature of the nuclear genome sets up an interesting genomic environment: the different genomic complements must interact with each other, and in the correct dosage. Our lab will use next-generation sequencing and cellular methods to identify and quantify the variety of genome dynamics that can occur in perpetual hybrid genomes, including mutation accumulation, gene silencing, and disrupted epistatic interactions.