• asexual reproduction;
  • automixis;
  • facultative parthenogenesis;
  • microsatellite DNA genotyping;
  • Reptilia;
  • Serpentes;
  • ZW sex-determination

In recent years genotyping analysis using mini- and microsatellite markers has provided robust DNA-based support for facultative parthenogenesis (FP) in several lineages of squamate reptiles (snakes and lizards) and sharks. Rather than incidental cases of reproductive error, there is growing evidence that FP is an alternative reproductive strategy and an important mode of reproduction in these phylogenetically divergent vertebrate groups. Because documentation of FP in vertebrates is in its infancy, additional instances supported by molecular genetic methods provide insights that advance our general understanding of this phenomenon. Here, in a female checkered gartersnake (Thamnophis marcianus) reared in isolation since a juvenile, we describe five successive parthenogenetic litters produced over a 7-year period that resulted in several viable male progeny. Cross species microsatellite amplification was performed across 30 primer pairs derived from Thamnophis spp. and related natricines to the female and nine available progeny. Five loci proved heterozygous in the maternal sample with the progeny differentially homozygous at all but one locus. Combined with evidence pertaining to captive history and litter characteristics, our analysis supports a specific type of FP, terminal fusion automictic parthenogenesis, over the competing hypothesis of long-term sperm storage. Importantly, we document that a single individual was capable of producing successive litters composed of live parthenogens. In two cases, males achieved adulthood and showed the anatomical potential to demonstrate reproductive competence (normal looking hemipenes and testes). © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 107, 566–572.