Parthenogenesis in squamates
Mechanisms
Parthenogenesis can result from either full cloning of the mother's genome, or through the combination of haploid genomes to create a "half-clone". Both mechanisms of parthenogenesis are seen in reptiles.
Full-cloning
Females can produce full clones of themselves through a modification of the normal
Half-cloning
Another mechanism typically observed in facultative parthenote reptiles is terminal fusion, in which a haploid
Types of parthenogenesis
True parthenogenesis
"True" parthenogenesis is a form of asexual reproduction in all-female species that produce offspring without any male involvement.[1]
Lizards
There are at least eight parthenogenetic species of Caucasian rock lizard in the genus Darevskia.[4][5] This genus is unique in containing the only known monoclonal parthenogenetic species, Darevskia rostombekovi, where the entire species originates from a single hybridization event. In all other cases of unisexual reptilian species that have been examined, multiple separate asexual lineages are present.[1] As true parthenotes, Darevskia do not require stimulation from sperm to reproduce.
The best-known and perhaps most evolutionarily derived example of parthenogenesis in reptiles occurs within the
There are six parthenogenetic
The fecundity of both parthenogenetic and sexual races of the gekkonid lizard Heteronotia binoei were compared.[10] These races occur together in areas of the Australian arid zone. Under laboratory conditions, the parthenogenetic geckos had about a 30% lower fecundity than their sexual progenitors.
Parthenotes are also found in two species of the
Snakes
The
Facultative parthenogenesis
Facultative parthenogenesis is the type of parthenogenesis when a female individual can reproduce via both sexual and asexual reproduction.[13] Females can produce viable offspring with or without genetic contribution from a male, and such an ability may, just like true parthenogens, enable colonization of new habitats by single female animals. Facultative parthenogenesis is extremely rare in nature, with only a few examples of animal taxa capable of facultative parthenogenesis, of which none are vertebrate taxa.[13]
Facultative parthenogenesis is often incorrectly used to describe cases of accidental or spontaneous parthenogenesis in normally sexual animals, including many examples in squamata.
Gynogenesis
Hybridogenesis
Hybridogenesis is a variation of parthenogenesis in which males mate with females, but only the mother's genetic material is propagated by these offspring to their own young. While this form of reproduction has not been observed in reptiles, it does occur in frogs of the genus Pelophylax.
Evolution
Origin
In all parthenogenetic reptile species studied to date, chromosomal evidence supports the theory that parthenogenesis arose through a
Selective advantage
While it is often assumed that parthenogenesis is an inferior evolutionary strategy to sexual reproduction because parthenogenetic species lack the ability to complement genetic mutations through outcrossing or are unable to incorporate new genetic material, research on parthenogenetic species has gradually revealed a number of advantages to this mode of reproduction. Triploid unisexual geckos of the species
References
- ^ .
- ^ Vitt, Laurie J., and Janalee P. Caldwell. Herpetology: an introductory biology of amphibians and reptiles. Academic Press, 2013.
- PMID 20173738.
- ^ Darevskii IS. 1967. Rock lizards of the Caucasus: systematics, ecology and phylogenesis of the polymorphic groups of Caucasian rock lizards of the subgenus Archaeolacerta. Nauka: Leningrad [in Russian: English translation published by the Indian National Scientific Documentation Centre, New Delhi, 1978].
- ^ Tarkhnishvili DN (2012) Evolutionary History, Habitats, Diversification, and Speciation in Caucasian Rock Lizards. In: Advances in Zoology Research, Volume 2 (ed. Jenkins OP), Nova Science Publishers, Hauppauge (NY), p.79-120
- ^ a b Moore, Michael C., Joan M. Whittier, and David Crews. "Sex steroid hormones during the ovarian cycle of an all-female, parthenogenetic lizard and their correlation with pseudosexual behavior." General and comparative endocrinology 60.2 (1985): 144-153.
- ^ PMID 21543715.
- ^ Bauer, A.M. (1994). "Familia Gekkonidae (Reptilia, Sauria) Part 1. Australia and Oceania". Das Tierreich. 109: xiii+306.
- PMID 18513934.
- ^ Kearney M, Shine R. Lower fecundity in parthenogenetic geckos than sexual relatives in the Australian arid zone. J Evol Biol. 2005 May;18(3):609-18. doi: 10.1111/j.1420-9101.2004.00866.x. PMID: 15842490
- ^ S2CID 15450879.
- ^ Wynn, Addison H., Charles J. Cole, and Alfred L. Gardner. "Apparent triploidy in the unisexual brahminy blind snake, Ramphotyphlops braminus. American Museum Novitates no. 2868." (1987).
- ^ ISBN 978-0-520-04583-5
- ^ PMID 26241141.
- S2CID 9137566.
- ^ Suomalainen E. et al. (1987). Cytology and Evolution in Parthenogenesis, Boca Raton, CRC Press
- ^ Lowe, Charles H., and John W. Wright. "Evolution of parthenogenetic species of Cnemidophorus (whiptail lizards) in western North America." Journal of the Arizona Academy of Science (1966): 81-87.
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