|The Desert Grasslands Whiptail, Aspidoscelis inornatus.|
In a new paper, Cole et al. (2017) describe the second known tetraploid amniote that reproduces by parthenogenetic cloning. This all-female species of whiptail lizard originated in the laboratory from hybridization between the Little Striped Whiptail, Aspidoscelis uniparens (triploid parthenogen) and the Desert Grasslands Whiptail, Aspidoscelis inornatus (diploid bisexual species). Similar clonal lineages of tetraploids arose from at least 44 F1 hybrid females. These were produced by at least 15 Aspidoscelis uniparens that mated with several different males of Aspidoscelis inornatus from both New Mexico and Arizona stock.
Inheritance of alleles at eight microsatellite deoxyribonucleic acid (msDNA) loci in the tetraploid species confirms its parentage, whereas DNA quantification and behavior of chromosomes in meiosis demonstrate that tetraploidy and heterozygosity are maintained generation after generation.
The authors compared univariate and multivariate variation in scalation between the tetraploids, their parental taxa, and four museum specimens from New Mexico that were reported as putative hybrids. Two of the putative hybrids are confirmed as such, but the other two are the Little Striped Whiptail, Aspidoscelis inornatus and the Desert Grasslands Whiptail, Aspidoscelis uniparens. The similarities of Aspidoscelis uniparens and the tetraploids suggest that tetraploid females may exist in old samples misidentified as Aspidoscelis uniparens. Clones of the tetraploid species are so similar to each other in morphology and msDNA that they authors could not distinguish most individuals or separate lineages from the P1 through multiple generations (up to F7) on the basis of the 12 msDNA loci analyzed in this study.
Discussion of the taxonomic aspects of the multiple hybrid origins of similar clones concludes that one specific name should be applied to all of them. For some systematists, depending on the species concept preferred, these lizards represent a complex of multiple cryptic species that cannot be reliably identified or diagnosed (one species for each F1 hybrid female that cloned a lineage). These specimens of known parentage provide valuable insights for the taxonomic treatment of natural parthenogenetic clones. In addition, the authors show that the degree of morphological variation in clonal parthenogens and bisexual Aspidoscelis inornatus can be similar to each other. They provide a new name for this new species, Priscilla’s Whiptail Lizard, Aspidoscelis priscillae.
Cole CJ, Taylor HL, Neaves WB, Baumann DP, Newton A, Schnittker R, Baumann P. The Second Known Tetraploid Species of Parthenogenetic Tetrapod (Reptilia: Squamata: Teiidae): Description, Reproduction, Comparisons With Ancestral Taxa, And Origins Of Multiple Clones. Bulletin of the Museum of Comparative Zoology. 2017 Oct 17;161(8):285-321.