Why is parthenogenesis not more common? Well, despite
the clear benefits outlined above, most parthenogenetic
organisms only enjoy short-term success. Although
hybridisation and polyploidy can inject genetic variation,
this occurs at a species or population level, and there is no
subsequent recombination. In fact, parthenogenesis entails
major drawbacks for genetic health. A key feature of
sexual reproduction is the mixing of genes between
individuals, which creates the genetic diversity required to
adapt to changes in the environment. For the individual,
having two different alleles of a given gene (i.e. being
heterozygous) can be advantageous: firstly, if an
individual is lumbered with a dodgy allele, the effects of
the dud may be masked by the other functional allele;
secondly, having two different versions of a gene can
translate to increased tolerance for a wider range of
conditions. Sexual reproduction also prevents inbreeding
depression, where an increasing number of individuals
share two deleterious alleles.
Reptile populations across the globe are dwindling, and
the fact that some species can, in times of desperation,
reproduce parthenogenetically offers a ray of hope in
some circumstances. However, given asexually-
reproducing organisms’ limited ability to adapt to envi-
ronmental changes, virgin births are unlikely to save many
species - more divine intervention may be required.
Further reading:
Abdala, C. S., Baldo, D., Juárez, R. A., & Espinoza, R. E. (2016). The
First Parthenogenetic Pleurodont Iguanian: A New All-female Liolaemus
‘
(Squamata: Liolaemidae) from Western Argentina. Copeia, 104(2), 487-
497, 411; retrieved from https://doi.org/10.1643/CH-15-381
Booth, W., & Schuett, G. W. (2011). Molecular genetic evidence for
alternative reproductive strategies in North American pitvipers
(Serpentes: Viperidae): long-term sperm storage and facultative parthe-
nogenesis. Biological Journal of the Linnean Society, 104(4), 934-942.
doi:10.1111/j.1095-8312.2011.01782.x
Booth, W., Schuett, G. W., Ridgway, A., Buxton, D. W., Castoe, T. A.,
Bastone, G., Bennett, C. & McMahan, W. (2014). New insights on facul-
tative parthenogenesis in pythons. Biological Journal of the Linnean
Society, 112(3), 461-468
Grismer, J. L., Bauer, A. M., Grismer, L. L., Thirakhupt, K., Aowphol,
A., Oaks, J. R., Wood, P. L. Jr., Onn, C. K., Neang, T., Cota, M. & Jack-
man, T. (2014). Multiple origins of parthenogenesis, and a revised spe-
cies phylogeny for the Southeast Asian butterfly lizards, Leiolepis. Bio-
logical Journal of the Linnean Society, 113(4), 1080-1093. doi:10.1111/
bij.12367
Lutes, A. A., Neaves, W. B., Baumann, D. P., Wiegraebe, W., &
Baumann, P. (2010). Sister chromosome pairing maintains heterozygos-
ity in parthenogenetic lizards. Nature, 464, 283. doi:10.1038/
nature08818
https://www.nature.com/articles/nature08818#supplementary-
information
Miller, K. L., Castañeda Rico, S., Muletz-Wolz, C. R., Campana, M. G.,
McInerney, N., Augustine, L., Frere, C., Peters, A. M. & Fleischer, R. C.
(2019). Parthenogenesis in a captive Asian water dragon (Physignathus
cocincinus) identified with novel microsatellites. PloS one, 14(6),
e0217489. doi:10.1371/journal.pone.0217489
Prendergast, Kit. 2016. “The all-female, globetrotting snake-in-a-pot!!:
The Brahminy Flowerpot Blind Snake (Ramphotyphlops braminus)”,
Odatria: Victorian Herpetological Society, October 2016, issue 19, pp. 7
-12
Shibata, H., Sakata, S., Hirano, Y., Nitasaka, E., & Sakabe, A. (2017).
Facultative parthenogenesis validated by DNA analyses in the green
anaconda (Eunectes murinus). PloS one, 12(12), e0189654. doi:10.1371/
journal.pone.0189654
‘
hatchling, together with tissue samples from the deceased
embryos, and sequenced the genes, along with those of the
mother. The results proved conclusively that the baby
dragon was produced by parthenogenesis.
The female water dragon started laying
eggs, despite being kept in an enclosure
without any males.
Asian or Chinese Water Dragon
(Physignathus cocincinus).
Image by PetlinDmitry.