Following the publication of increasing numbers of studies over recent years, facultative parthenogenesis has been removed from the realm of obscurity and placed firmly in a position where it now warrants focused scientific attention. Until recently facultative parthenogenesis, the ability for a sexually reproducing species to reproduce asexually, has been considered an evolutionary novelty, confined to captive specimens and thus attributed as a captive syndrome. With the abundance of papers now confirming facultative parthenogenesis across a diverse array of species, namely birds, sharks, and several lineages of non-avian (squamate) reptiles (lizards and snakes), such opinions are changing. Indeed, with the recent detection of facultative parthenogenesis in two natural populations of North American pitviper snake, the paradigm is now shifting to consider facultative parthenogenesis a potentially important aspect of vertebrate evolution. As such, species capable of facultative parthenogenesis may represent ideal model organisms for understanding the evolution and maintenance of sex. It is therefore important to understand fully the distribution of FP within phylogenies, to understand the subtle variations and commonalities that may exist across species, and to identify the conditions and proximate mechanisms by which the “sexual-asexual switch” is accomplished.
Within the lab we have recently documented facultative parthenogenesis in a number of snakes, ranging from the basal Boa constrictor to the advanced Copperhead, Agkistrodon contortrix. This research has upended decades of scientific theory with the discovery of viable WW sex-chromosome females, a condition considered non-viable since the 1950's. Additionally, we have documented the first, and to date only, cases of facultative parthenogenesis within natural, wild populations. This was documented in two closely related species of North American pitviper. Our work continues with the documentation of parthenogenesis across the squamate phylogeny, and is now taking a genomic approach to understand the genetic mechanisms by which this alternative reproductive strategy is achieved.