quote: For example, Gerhardt has identified a case in which a single species of Hyla tree frogs has undergone tetraploid formations. The formation of tetraploid (4n) from the fusion of two diploid parents (2n) leads to a new species of treefrog that can only breed with another individual that has similar ploidy (Gerhardt 198X). The fusion of gametes from a diploid parent and tetraploid parent produces triploid offspring which die during larval stages and the few hybrids that reach adult size are sterile (Johnson. While production of triploids can be achieved in the laboratory, triploids are rarely found in natural populations of Hyla tree frogs (Gerhardt 1982).
Because the diploid parental species achieves reproductive isolation from the tetraploid daughter species in one fell-swoop, sympatric speciation is easy to achieve. Indeed Gerhardt and his colleagues have found that the production of new tetraploid species has occurred several times in this species complex. Diploid populations of Hyla chrysoscelis probably gave rise to tetraploid populations of H. versicolor (Tymowska 1991).
So there is a species that is the offspring of a different species. What fascinates me is whether the tetraploid frog could undergo parthenogenesis and produce a haploid child. A haploid of a tetraploid would be a diploid- and a member of the original species. Parthenogenesis doesn't appear to be associated with any particular species of frog. What an interesting system. I can't believe they got a rabbit to parthogenize.
However, it is typically assumed that parthogenetic offspring are clones, when some genetic exchange occurs during gamete formation. So while the offspring will only have genes from the mother, they will not have all the mother's genes.
Example: I have B blood, with a recessive O. If I produce an egg with the recessive O then the offspring will have O blood. As a matter of fact, all four of my children have had O blood.
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The diploid offspring would only be a descendant of the original species if it were relatively soon (in a geologic/evolutionary sense) after the speciation event. Otherwise, the genome could well have diverged enough to prevent reintegration.
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I believe this has also been observed in the Australian wallaby, which has about ten distinct species in a fairly small geographical area. So much for 'no transitional forms', eh?
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Noemon
