The desert grassland whiptail lizard (''Aspidoscelis uniparens'') is an all-female species of reptiles in North America. It was formerly placed in the genus ''

Cnemidophorus ''Cnemidophorus'' is a genus of lizards in the family Teiidae. Species in the genus ''Cnemidophorus'' are commonly referred to as whiptail lizards or racerunners. The genus is native to South America, Central America, and the West Indies. Tax ...

''. A common predator of the whiptail lizard is the leopard lizard that preys on ''A. uniparens'' by using ambush and stalk hunting tactics. These reptiles reproduce by

parthenogenesis Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertiliz ...

. In this process, eggs undergo a

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

doubling after

meiosis Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one c ...

, developing into lizards without being

fertilized Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or off ...

. However,

ovulation Ovulation is an important part of the menstrual cycle in female vertebrates where the egg cells are released from the ovaries as part of the ovarian cycle. In female humans ovulation typically occurs near the midpoint in the menstrual cycle and ...

is enhanced by female-female courtship and mating (pseudo-copulation) rituals that resemble the behavior of closely related species that reproduce sexually.

Description

The desert grassland whiptail lizard is a relatively small reptile, whose size ranges from . 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. 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 The Lacertidae are the family of the wall lizards, true lizards, or sometimes simply lacertas, which are native to Afro-Eurasia. It is a diverse family with at about 360 species in 39 genera. They represent the dominant group of reptiles found ...

. Soon after, researchers discovered that there were also no males in ''C. exsanguis'', ''C. neomexicanus'', or ''C. velox''. 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.

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 Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, game reserves, or nature ...

. ''A. uniparens'' are scarce in developed areas, especially where homeowners keep livestock.

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. The lizards reproduce by parthenogenesis and are 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. 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.Eifler DA, Eifler MA (1998) Foraging Behavior and Spacing Patterns of the Lizard ''Cnemidophorus uniparens''. J Herpetol 32:24–33 A smaller portion of their diet includes prey found above ground such as grasshoppers and butterflies.

Description

Taxonomy

Habitat

Hybridization and reproduction

Food habits

References

Further reading