Desert grassland whiptail lizard

Desert Grassland Whiptail
Conservation status
	; Least Concern (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Family:	Teiidae
Genus:	Aspidoscelis
Species:	A. uniparens
Binomial name
	Aspidoscelis uniparens; (Wright & Lowe, 1965)
Synonyms
	Cnemidophorus uniparens Wright & Lowe, 1965

The desert grassland whiptail lizard (Aspidoscelis uniparens) is an all-female species of reptiles. It was formerly placed in the genus Cnemidophorus. A common predator of the whiptail lizard is the leopard lizard, that prey on A. uniparens by using ambush and stalk haunting tactics.[2][3][4] These reptiles reproduce by parthenogenesis. In this process, eggs undergo a chromosome doubling after meiosis, developing into lizards without being fertilized. However, ovulation is enhanced by male-male courtship and "mating" (pseudo-copulation) rituals that resemble the behavior of closely related species that reproduce sexually.[5][6][7]

Description

The desert grassland whiptail lizard is a relatively small reptile, whose size ranges from 2¾ inches (6.9 cm) to 5¼ inches (13.3 cm).[8] Desert grassland whiptails are very long and slim, with a thin tail that is longer than their body length. Their distinct identifying feature are the six yellowish lines that run the length of their body. The majority of the whiptail's body tends to be an olive or brown colour that fades to a faint blue or gray on their tail. Comparatively, an adolescent's tail is a very bright and vibrant blue.[9] Their bodies are lined with small coarse scales, which gradually get larger as they approach the tail. The scales on their bellies are much larger in size and are much smoother as well.

Taxonomy

The taxonomy of the genus was unknown until the 1950s to early '60's. A 1958 report confirmed that no male lizards had been discovered in a collection of specimens of C. tesselatus. That very year, parthenogenesis was confirmed in the genus Lacerta of the family Lacertidae. Soon after, researchers discovered that there were also no males in C. exsanguis, C. neomexicanus, or C. velox.[10] Rather than subsume all cnemidophorine species into a single large genus, Lowe and Wright proposed a split that placed the North American "Cnemidophorus" clade in the monophyletic genus Aspidoscelis. Under this arrangement, South American taxa remain in the genus Cnemidophorus.[1]

Habitat

The desert grassland whiptail is mostly found in the deserts of southern to central Arizona and along the Rio Grande river in New Mexico. It is also found in the deserts of northern Mexico. A. uniparens is commonly found in low valleys, grasslands, and slight slopes. Some have argued that the species' range is expanding due to overgrazing. A. uniparens are scarce in developed areas, especially where homeowners keep livestock.[11]

Hybridization and reproduction

All desert grassland whiptail lizards are female. Their reproduction process does not need male fertilization, although researchers observed pseudo-copulation that promotes fertilization during ovulation. This process involves the alternation between male-typical and female-typical sexual behaviours, driven by progesterone, in both lizards; corresponding to the state of their partner.[12] The lizards reproduce by parthenogenesis, but offspring are not necessarily clones of their mother. Under normal reproductive processes, a species has each chromosome pair separated, copied, and paired back with its counterpart. The desert grassland whiptail lizard, however, has chromosome triplets where each triplet is paired with its copy rather than its counterparts. This reproductive method enables the asexual desert grassland whiptail lizard to have a genetic diversity previously thought to have been unique to sexually reproductive species.[13]

The lizards were a result from a cross breed of two bisexual species, A. inornata and A. burti. This then produced a diploid unisexual, which backcrossed to inornata and produced triploid uniparens.

Food habits

For the most part, the Desert grassland whiptail digs for termites, Queen ants, beetles, and unidentified insects.[14] A smaller portion of their diet includes prey found above ground such as grasshoppers and butterflies.

References

Hammerson, G.A. & Santos-Barrera, G. (2007). "Aspidoscelis uniparens". IUCN Red List of Threatened Species. 2007: e.T64291A12754846. doi:10.2305/IUCN.UK.2007.RLTS.T64291A12754846.en.
Tollestrup K (1983) The social behavior of two species of closely related leopard lizards, Gambelia silus and Gambelia wislizenii. Z Tierpsychol 62:307–320
Pietruszka RD (1986) Search tactics of desert lizards: how polarized are they? Anim Behav 34:1742–1758
Eifler, D. A., Eifler, M. A., & Harris, B. R. (2008). Foraging under the risk of predation in desert grassland whiptail lizards (Aspidoscelis uniparens). Journal of Ethology, 26(2), 219-223. doi:10.1007/s10164-007-0053-0
Crews, D. & Fitzgerald, K.T. (1980). "Sexual" behavior in parthenogenetic lizards (Cnemidophorus). Proceedings of the National Academy of Sciences, 77, 1. pp. 499-502.
Crews, D., Grassman, M. & Lindzey, J. (1986). Behavioral Facilitation of Reproduction in Sexual and Unisexual Whiptail Lizards. Proceedings of the National Academy of Sciences, 83, 24. pp. 9547-9550.
Grassman, M. & Crews, D. (1987). Dominance and reproduction in a parthenogenetic lizard. Behavioral Ecology and Sociobiology, 21. pp. 141-147.
"Whiptails (Cnemidophorus Spp.)." https://www.desertmuseum.org/books/nhsd_whiptails.php. Ed. Craig Ivanyi. Arizona-Sonora Desert Museum, 1 Jan. 2014. Web. 23 Oct. 2014.
Brennan, Thomas C. "Desert Grassland Whiptail (Aspidoscelis Uniparens) - Reptiles of Arizona." Reptiles of Arizona. Reptiles of Arizona. Web. 23 Oct. 2014.
Lowe, Charles H., 1993. Introduction to the biology of whiptail lizards (genus Cnemidophorus) . “Biology of Whiptail Lizards (Genus Chemidophorus)”
Audsley, Blake. American Midland Naturalist Volume: 155 Issue: 2 (2006-04-01) p. 395-401. ISSN 0003-0031
Crews, David (1987). "Courtship in unisexual lizards: A model for brain evolution". Scientific American. 257 (6): 116–121. doi:10.1038/scientificamerican1287-116.
Harmon Katherine (2010) No Sex Needed: All-Female Lizard Species Cross Their Chromosomes to Make Babies. www.scientificamerican.com/article/asexual-lizards/
Eifler DA, Eifler MA (1998) Foraging Behavior and Spacing Patterns of the Lizard Cnemidophorus uniparens. J Herpetol 32:24–33