by Greg Mayer
Not much in the way of culinary pleasures here. (Although Jerry’s piece on the Inquisition killed my appetite, anyway). Reader Pete Moulton asked for some references on hybridization and parthenogenesis in whiptail lizards (Cnemidophorus [or Aspidoscelis] and related teiid lizards), in particular C. (A.) uniparens.
A. uniparens is a triploid unisexual. It resulted from a cross of two bisexual species (A. inornata [mother] and A. burti [father]), which produced a diploid unisexual, which then backcrossed to inornata to produce the triploid uniparens. The unisexuals reproduce clonally, i.e. offspring are exact genetic copies of their mothers, except for new mutations. Courtship and ‘pseudocopulation’ between parthenogenetic females promotes reproduction. The situation is summarized nicely by Cole et al. (2010):
The natural origin of diploid parthenogenesis in whiptail lizards has been through interspecific hybridization. Genomes of the parthenogens indicate that they originated in one generation, as the lizards clone the F1 hybrid state. In addition, hybridization between diploid parthenogens and males of bisexual species has resulted in triploid parthenogenetic clones in nature. Consequently, the genus Aspidoscelis contains numerous gonochoristic (= bisexual) species and numerous unisexual species whose closest relatives are bisexual, and from whom they originated through instantaneous sympatric speciation and an abrupt and dramatic switch in reproductive biology.
The selection of papers below includes both classics and recent papers, with a preference towards ones where online full text was available (see pdf links below). These papers are all about whiptails of the family Teiidae. Laurie Vitt and Jana Caldwell, in their fine text Herpetology (Academic Press 2009), record about 50 species of parthenogenetic lizards (adding in a few they missed) in eight families (including the whiptails), and one species of parthenogenetic snake.
Wright, J.W. and C.H. Lowe. 1968. Weeds, polyploids, parthenogenesis, and the geographical and ecological distribution of all-female species of Cnemidophorus. Copeia 1968: 128-138. no pdf (A classic on unisexual ecology.)
Parker, E.D. and R.K. Selander. 1976. The organization of genetic diversity in the parthenogenetic lizard Cnemidophorus tesselatus. Genetics 84:791-805. pdf (A classic on unisexual genetics.)
Crews, D. and K.T. Fitzgerald. 1980. “Sexual” behavior in parthenogenetic lizards (Cnemidophorus). Proceedings of the National Academy of Science USA 77: 499-502. pdf (A classic on unisexual behavior.)
Reeder, T.W., H.C. Dessauer, and C.J. Cole. 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 3365:1-62. pdf (In this paper, the genus Aspidoscelis is resurrected for part of the genus Cnemidophorus; because there is such a huge literature under the name Cnemidophorus prior to 2002, both names must be used when searching the literature. The part on hybrid origin begins on page 25.)
Cole, C.J., L.M. Hardy, H.C. Dessauer, H.L. Taylor, and C.R. Townsend. 2010. Laboratory hybridization among North American whiptail lizards, including Aspidoscelis inornata arizonae × A. tigris marmorata (Squamata: Teiidae), ancestors of unisexual clones in nature. American Museum Novitates 3698:1-43. pdf
The American Museum of Natural History’s Digital Library has pdf’s of all the Museum’s publications, and it has been a center for studies of parthenogenetic lizards. More papers can be found by going to the Digital Library site and searching on ‘Cnemidophorus’, ‘Aspidoscelis’, and ‘parthenogenesis’.
UPDATE. The numbers of parthenogenetic species of lizards and snakes compiled by Vitt and Caldwell and given above refers only to obligately (or nearly so) parthenogenetic species, not facultatively parthenogenetic ones (like Komodo dragons, boa constrictors, and some other snakes; they have a separate discussion of the facultative species in their book).