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MegF42 wrote:

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Just because they live in the same area, doesn't mean they would interbreed. You can get a cornsnake and a king to happily breed too, but they don't do it in the wild. So far, I've yet to see any carpondros paired together produce any viable offspring....I've seen plenty of carpondro/chondro, or carpet/chondro pairings though. Has anyone produced viable offspring from carpondro/carpondro?

No, it doesn't mean they will hybridize, BUT being sympatric makes the scenario at least enter the realm of possibility, compared to say a natural Aru x Biak mating. Okay, a natural Aru x Biak is theoretically possible via rafting, but if you look at a map of Indo the chances of a M. viridis x spilota hybrid are far more likely.

In 2006 a natural polar bear grizzly bear hybrid was documented. Hybrids of this type had previously been documented in captivity, but most people thought it would never happen in nature (that is until they found a hybrid in nature). Ambystoma jeffersonianum regularly hybridize with Ambystoma laterale in nature. Hybridization is not unheard of in nature and can actually be quite common. The first requirement is that the two species have the ability to come into contact with one another in nature. After speaking to Rob Heinsohn I know that at least in Australia, M. spilota and M. viridis do indeed have opportunities to come into contact with one another. Do they hybridize? Well, it's been documented in captivity, but not in nature (kind of like polar bear x grizzly bear hybrids were thought of . . . until 2006).

I also have not heard of a successful "carpondro" x "carpondro" pairing. If hybrid M. viridis x spilota occur in nature I don't imagine they would be common so it would be far more likely for a hybrid to encounter either parental species, which we know the hybrids can reproduce with. This is where it gets interesting since seemingly "pure" chondros or carpets could indeed have genetic influence from another species from a mating many generations removed. Once those genes are in the gene pool they could hang around quite some time.

Will

cnewsom wrote:

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Has anyone thought that prezygotic isolation/barriers [read: pressures] (obviously reproductive organ incompatability is out the window via capture hybridization knowledge) might be stronger in the wild, ignoring our obsession of placing 2+ captive, horomone raging ________ (fill in the 'captive animal(s)' here) together, than that of the captive environment; and thus greatly reducing the lightning-strike lottery odds of certain species producing a 'natural' hybrid?

As you mentioned, with M. viridis and M. spilota we can rule out mechanical isolation since we know the reproductive organs between these species are compatible. We can rule out gametic isolation since we know hybrids can be produced. This leaves behavioral isolation, which I think is what you were getting at. There likely are behavioral isolation barriers between the M. viridis and M. spilota in nature, but there were also thought to be strong behavioral isolation barriers that would prevent any natural hybridization between polar bears and grizzly bears. Here's more on that:

"I don't think anyone expected it to actually happen in the wild," said Ian Stirling, a polar bear expert with the Canadian Wildlife Service in Edmonton. Polar bears and grizzlies require an extended mating ritual to reproduce, Stirling said. Both live by themselves in large, open habitats. To prevent wasting their eggs, females ovulate only after spending several days with a male, Stirling explained. "Then they mate several times over several days." In other words, the mating between the polar bear and grizzly was more than a chance encounter.

Gametic and mechanical isolation barriers work pretty well, but behavioral barriers don't always work and hybrids are the result. Even if hybridization occurred only once in nature between M. viridis and M. spilota, such an event would give those "foreign" genes a doorway to becoming part of gene pool of a particular population of GTPs (or Carpets). That's what I find interesting. What influence would these genes have? Would the genes just be absorbed and diluted through the gene pool through multiple generations? Would they show an influence many generations removed? Fascinating stuff.

Will