Abstract
Facultative parthenogenesis (FP) is widespread in the animal kingdom. In vertebrates it was first described in poultry nearly 70 years ago, and since then reports involving other taxa have increased considerably. In the last two decades, numerous reports of FP have emerged in elasmobranch fishes and squamate reptiles (lizards and snakes), including documentation in wild populations of both clades. When considered in concert with recent evidence of reproductive competence, the accumulating data suggest that the significance of FP in vertebrate evolution has been largely underestimated. Several fundamental questions regarding developmental mechanisms, nonetheless, remain unanswered. Specifically, what is the type of automixis that underlies the production of progeny and how does this impact the genomic diversity of the resulting parthenogens? Here, we addressed these questions through the application of next-generation sequencing to investigate a suspected case of parthenogenesis in a king cobra (Ophiophagus hannah). Our results provide the first evidence of FP in this species, and provide novel evidence that rejects gametic duplication and supports terminal fusion as a mechanism underlying parthenogenesis in snakes. Moreover, we precisely estimated heterozygosity in parthenogenetic offspring and found appreciable retained genetic diversity that suggests that FP in vertebrates has underappreciated evolutionary significance.
Highlights
Facultative parthenogenesis (FP) is widespread in the animal kingdom
Most published studies on the phenomenon of facultative parthenogenesis (FP) have not been sufficiently robust to accurately differentiate between these two developmental mechanisms and provide little opportunity to examine secondary questions focused on how genetic variation is inherited in parthenogenetic offspring, and the impact parthenogenesis may have on the evolutionary trajectories of natural populations[8,25]
We provide the first in-depth, genome-wide assessment of genetic diversity for a squamate reptile reproducing via FP, through the comparison of two parthenogenetic male king cobra siblings with their mother
Summary
Facultative parthenogenesis (FP) is widespread in the animal kingdom. In vertebrates it was first described in poultry nearly 70 years ago, and since reports involving other taxa have increased considerably. Most published studies on the phenomenon of FP have not been sufficiently robust to accurately differentiate between these two developmental mechanisms and provide little opportunity to examine secondary questions focused on how genetic variation is inherited in parthenogenetic offspring, and the impact parthenogenesis may have on the evolutionary trajectories of natural populations[8,25] With such indeterminate outcomes, understanding which mechanism of automixis is operating has important implications on the levels of genetic diversity retained in parthenogenetic offspring, which in turn has major ramifications for understanding the impact that these parthenogens might have on the genetic diversity of natural populations. Despite advances that recent studies have made towards understanding FP in vertebrates[9], the fundamental questions of: (i) resolving which automictic mechanism(s) underlie FP, and (ii) how FP impacts individual-level genetic diversity on a genome-scale, remain unresolved
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