Re: Asexual reproduction in reptiles

The group of lizards you refer to, the whiptails of the south-western US,
have fascinated zoologists and geneticists for years.  Of the 11 or so 
whiptail species, about one-third are unisexual, reproducing by 
parthenogenesis, or development of an unfertilized egg.  While I have not
studied these lizards myself in the field, I would not identify the
unisexual forms as subspecies, since they cannot interbreed with 
sexually reproducing closely related groups.  I would tend to call
each a separate species. There are probably herpetologists that would 
disagree with that classification, however.

The mechanism of reproduction among the unisexual species seems to
involve production of haploid eggs by females (which is quite normal).
The eggs develop, however, without fertilization by sperm, and 
chromosomes double at some point to create diploid adults.  This doubling 
of chromosomes does not allow any new rearrangements of genetic 
information, so all offspring are genetically identical ("a clone") of 
the previous generation.  

At least a couple of these unisexual species have been identified as 
hybrid offspring resulting from the mating of two other species of
normal whiptails.  For example, the unisexual New Mexico whiptail 
(Cnemidophorus neomexicanus) appears to be the result of a crossbreeding
of the western whiptail (C. tigris) and the little striped whiptail
(C. inornatus).  Sexual reproduction seems to work normally in the latter
two species.

Check in a good field guide to see pictures of these and related whiptails.
A good scientific reference to this field of study is:
"Unisexual Lizards," by C.J. Cole, in _Scientific American_,
Jan. 1984, pp. 94-100.
See also "Parthenogenesis in Lizards" in Nov/Dec. '89 issue of
_Reptiles & Amphibians Magazine_