Unisexual reproduction in Vertebrates - Developing Genomic Tools to Study Hybridization, Ploidy Changes and Diversity in “Clonal” Lineages.

Historic hybridization events between different species of whiptail lizards (genus Aspidoscelis) gave rise to rare hybrids with the ability to reproduce clonally by true parthenogenesis.  Such clones have colonized large parts of the American Southwest over the course of hundreds or thousands of generations.  Cytological analysis has begun to shed light on how the program of oogenesis is modified to permit fundamentally different modes of reproduction in closely related species.  In parthenogenetic females, oocytes contain four instead of two sets of chromosomes. The pairing and recombination between homologous chromosomes is replaced by the pairing of identical chromosomes.  The two meiotic divisions then generate a diploid instead of haploid egg that does not require fertilization to restore the somatic chromosome number.  How the chromosome number is doubled and how homolog pairing is suppressed are still unclear.

To gain further insights into the biology of parthenogenesis in vertebrates we are developing genomic tools for comparative studies.  Dovetail’s Chicago libraries and HiRise assemblies were instrumental in generating high quality assemblies for three sexually reproducing species that hybridized in the past to produce at least two parthenogenetic species.  We will discuss the progress in establishing a reference genome for Aspidoscelis tigris as well as recent insights gained from genomic analysis.