The role and history of pitvipers in our understanding of facultative parthenogenesis and long-term sperm storage in females

Booth, Warren

warrenbooth@vt.edu

Department of Entomology                                                                                                                           

Virginia Polytechnic Institute and State University                                                                                 

Blacksburg, Virginia USA

Facultative parthenogenesis (FP), a fairly recent alternative hypothesis to long-term sperm storage (LTSS), is a seemingly rare reproductive phenomenon in which females that normally reproduces sexually produce offspring without male genetic contribution via sperm. In snakes, FP has been increasingly documented across multiple taxa since 1997, including pitvipers. While once considered a biological curiosity or artifact of captivity, findings in wild populations suggest FP may serve as an adaptive reproductive strategy, potentially under conditions of mate scarcity or environmental stress. This mode of reproduction results in offspring that exhibit near-genome-wide homozygosity due to the assumed mechanisms of terminal fusion automixis. Recent genomic studies have revealed insight into the underlying mechanisms of diploidy restoration. However, offspring viability and fitness can be compromised due to inbreeding-like genetic outcomes. The ecological and evolutionary implications of FP in snakes remain under investigation, particularly its role in population persistence, genetic diversity, and species resilience. Continued research using genomic tools and long-term field monitoring is essential to determine the frequency, triggers, and consequences of FP in natural populations. Understanding the importance of FP in snakes will likely shed light on broader evolutionary questions surrounding sexual and asexual reproduction in vertebrates.