What are the Phenotypic Consequences of Reproduction by Facultative Parthenogenesis? An Assessment of Venom Composition and Function from the Copperhead (Agkistrodon contortrix)
Casewell, Nicholas R.
Alistair Reid Venom Research Unit
Liverpool School of Tropical Medicine
Calvete, Juan J.
Laboratorio de Venómica Estructural y Funcional
Instituto de Biomedicina de Valencia, CSIC
Facultative parthenogenesis is asexual reproduction in species that would otherwise reproduce sexually. Recent reports of facultative parthenogenesis occurring in natural vertebrate populations (pitvipers), combined with the recent demonstration that parthenogens can show reproductive competence, indicate that this mode of reproduction has important evolutionary consequences and implications. Facultative parthenogenesis results in progeny that are half-clones of the mother as the result of automictic development, resulting in dramatic reductions in heterozygosity. Consequently, the implications on key phenotypic characters seem likely to be significant, yet remain (almost) completely unstudied. Many lineages of snakes produce and use venom to subjugate prey; thus, this character is tightly linked to individual fitness. In this study, we assessed the phenotypic consequences of facultative parthenogenesis on the composition and function of venom collected from copperhead snakes (Viperidae: Agkistrodon contortrix), including a male parthenogen, its mother, and individuals from the same population. To do so, we used a variety of proteomic approaches, underpinned by venom gland transcriptome data, and a suite of in vitro biochemical assays. Our results demonstrate a degree of variation in both venom composition and function; however, overall they suggest that the apparent loss of genomic diversity resulting from facultative parthenogenesis does not result in a major loss of venom toxin complexity or functional activity, and consequently may not have a significant impact on the prey-capturing ability in venomous snakes produced via facultative parthenogenesis.