Hybridization and parthenogenesis in whiptail lizards

November 19, 2010 • 12:26 am

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.

Desert grassland whiptail, by Davepape from Wikipedia.

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).

That lizard was delicious– what kind was it?

November 18, 2010 • 11:21 am

by Greg Mayer

That’s more or the less the question Ngo Van Tri, a Vietnamese herpetologist, must have asked himself after having a meal like that shown below, which surely rivals anything Jerry’s had in Colombia.

Leiolepis ngovantrii. From Lee Grismer, via The Independent.

Tri contacted Lee Grismer of La Sierra University and his son Jesse Grismer, a graduate student at Villanova University, both herpetologists. They went to Vietnam and found that it was an undescribed species, which they named Leiolepis ngovantrii in Tri’s honor, in a paper (whose title oddly brings to mind the 2003 Red Sox) published this past spring in Zootaxa (abstract only).

All new species are interesting, but new ones are found all the time. What makes this one especially of note (besides being discovered on a dinner plate) is that it is a parthenogenetic species– consisting only of females, and reproducing asexually. This is a rather unusual mode of reproduction in vertebrates, but a fair number of lizards, including species in the families Teiidae, Lacertidae, Geckonidae, and (like Leiolepis) Agamidae, reproduce this way. Most parthenogenetic lizard species have arisen by hybridization between two sexual species. The Grismers, using mitochondrial DNA, have been able to identify the maternal parent species of L. ngovantrii, and also of the three other parthenogenetic species of Leiolepis, showing that parthenogenesis in this genus has arisen in the usual way for lizards. It’s also known to occur spontaneously in normally sexual species, such as the Komodo dragon, Varanus komodoensis.

The unusual method of discovery has attracted some media attention.

(And, I should mention that Lee Grismer is the author of one of the best “Animals of___” books ever: the magnificent Amphibians and Reptiles of Baja California, Including Its Pacific Islands and the Islands in the Sea of Cortés, University of California Press, 2002).

Grismer, J. and L.L. Grismer. 2010. Who’s your mommy? Identifying maternal ancestors of asexual species of Leiolepis Cuvier, 1829 and the description of a new endemic species of asexual Leiolepis Cuvier, 1829 from Southern Vietnam. Zootaxa 2433:47-61.

h/t: Steve Orzack, Fresh Pond Research Institute