Aspidoscelis

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Aspidoscelis is a genus of whiptail lizards in the family Teiidae.

Taxonomy

The nomenclature for the genus Aspidoscelis was published by T.W. Reeder et al. in 2002. Many species that were formerly included in the genus Cnemidophorus are now considered Aspidoscelis based upon divergent characters between the two groups.

Etymology

The name Aspidoscelis literally means "shield-leg", from the Ancient Greek [[wikt:ἀσπίς|Template:Transliteration]] ("shield") and [[wikt:σκέλος|Template:Transliteration]] ("leg").[1]

Species

The following species are recognized as being valid.[2][3]

Nota bene: A binomial authority in parentheses indicates that the species was originally described in a genus other than Aspidoscelis.

Speciation

In 2011, it was announced that a parthenogenetic hybrid Aspidocelis was bred in the laboratory.[4] This serves as a demonstration of how other hybrid parthenogens in this genus may have arisen.

Parthenogenesis and unisexual species

Thirteen species within Aspidoscelis are unisexual, consisting entirely of females that reproduce through parthenogenesis—cloning unfertilized eggs to produce genetically identical offspring.These species originated through hybridization between divergent bisexual ancestral species, with the transition to asexual reproduction occurring in a single generation. This represents the largest group of unisexual vertebrate species known to science.[5]

The unisexual species exhibit varying chromosome numbers reflecting their hybrid origins. Diploid species formed through "primary hybrid speciation" when first-generation female hybrids of two distinct bisexual species began reproducing parthenogenetically. Triploid and tetraploid species arose through "genome addition," when cloned eggs of unisexual females were fertilized by males of bisexual species, resulting in offspring with additional chromosome sets.[5]

This hybridization seesm separated by 15–25 million years of evolution. The parental species combinations have been determined through karyotypic, allozyme, and mitochondrial DNA studies. Early chromosome studies in the 1960s first revealed abnormal chromosome numbers in some unisexual species, indicating genome combinations from divergent species through hybridization.[5]

The unisexual species occur in two main geographic regions: the southwestern United States and northern Mexico, and southern Mexico with eastern Guatemala and Belize. Recent cellular research has revealed that chromosome number and genetic diversity are maintained across generations because identical, duplicated chromosomes pair during meiosis rather than homologous chromosomes.[5]

References

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Further reading

  • Fitzinger L (1843). Systema Reptilium, Fasciculus Primus, Amblyglossae. Vienna: Braumüller & Seidel. 106 pp. + indices. (Aspidoscelis, new genus, p. 20). (in Latin).

External links

  • Reeder, Tod W.; Cole, Charles J.; Dessauer, Herbert C. (2002). "Phylogenetic relationships of whiptail lizards of the genus Cnemidophorus (Squamata, Teiidae) : a test of monophyly, reevaluation of karyotypic evolution, and review of hybrid origins". American Museum Novitates (3365): 1-61. [1]


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  3. Genus Aspidocelis at The Reptile Database. www.reptile-database.org.
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