>Hello Greg,
>Parker and Selander (in a 1976 Genetics article) did find variation in
>Cnemidophorus tesselatus genotypes (using allozyme electrophoresis)
>and attributed it to three things:
>1)post-formation mutation
>2)recombination events (right on, Greg!)
>3)multiple hybridization events
There is also very high genetic diversity among parthenogenetic Bynoe's geckos. Craig Moritz found that at some rubbish dumps in Central Australia (the best habitat to find them in), you can catch 6 geckos, type them using allozymes, and find that you have 6 different types of parthenogen! At other sites there was less diversity. The vast majority of this variation is thought to be the result of multiple hybridization events. The parthenogens originated when two sexual lineages of Bynoe's gecko, soon to be described, hybridized. This seems to have happened in a very limited area in Western Australia and the parthenogens have since spread south and east across the country. The different types of parthenogen are the result of different sexual parents mating within this limited geographic area (i.e. multiple hybridization events). However, when a given type of parthenogen reproduces, she clones herself, so the diversity within parthenogenetic lineages is low but the diversity among the lineages is very high. BYW, all the different types of parthenogenetic Bynoe's geckos fall within two different mitochondrial lineages of parthenogen and these will soon be given the status of "species".
Moritz also found parthenogenenic lineages which appear to be the result of novel mutations, and he also said to me that it is theoretically possible (but unlikely) for recombination to occur in parthenogens (but I'm not sure how). The mechanism of parthenogenesis in Whip-tails is called "premeiotic endomitosis", which is simply a doubling of chromosomes before meiosis starts, i.e. an internal mitosis. This means that crossing over has no effect because it occurs between identical chromosomes, and it also means that random segregation has no effect either.
Also, with regards to evolutionary dead ends, there is good evidence that parthenogenetic Bynoe's geckos are more susceptible to infection by little red mites than their sexual relatives where they co-occur. When I was collecting my animals this was amazingly apparent - in some places the parthenogens would often have so many red mites around their eyes that they looked like they had goggles on (!) whereas the sexuals found side-by-side with them were "clean". This supports the "Red Queen Hypothesis" for the advantage of sex (i.e. that sex results in increased genetic variation which makes animals more competitive in evolutionary "arms races" between them and their parasites). In the long run, this disadvantage faced by the parthenogens may tip the balance in favour of the sexual geckos. In the short term, however, the parthenogens are thriving and there are indeed millions of them under bits of tin, old washing machines, 44 gallon drums, car bonnets etc. etc. in the deserts of Australia. (BYW, a short article on the collecting trip I did, with some pics, is at http://www.bio.usyd.edu.au/Newslett/Archive/2000/December.htm
).
Greg - I would love to learn more about the parthenogenetic blind snake you mentioned earlier. Do you have any good refs? If so could you e-mail them to me privately? Many thanks.
best regards (and happy new year),
Michael
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Michael Kearney
School of Biological Sciences
Building A08
University of Sydney
NSW, AUSTRALIA, 2006
[EMAIL PROTECTED]
ph + 61 2 9351 7661
fax + 61 2 9351 5609
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