Speciation of Introduced Herps

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FunkyRes
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Speciation of Introduced Herps

Post by FunkyRes »

As I'm sure everyone is aware, last couple of hundred years has seen the successful introduction of numerous herp species all over the world into habitat the species did not and probably would not reach on its own.

Here in CA the prime examples are probably American Bullfrogs and Red-eared Sliders. In both those cases, I don't believe there is population reproductive isolation, at least not in urban areas. They may not frequently send representatives back to native range (though maybe Bullfrogs do) but they certainly still receive gene flow from native range via pet trade / food trade.

But there are undoubtedly populations of some species that are reproductively isolated and may at some point speciate into distinct taxon. How long that may take I can't even begin to guess at, but it got me wondering, how often has it already happened?

We know Polynesians often brought geckos with them. Are there any species of Geckos that are thought to have found their new homes originally as a different species brought there by human technology? Other species that may have speciated since a human introduction?

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Gluesenkamp
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Re: Speciation of Introduced Herps

Post by Gluesenkamp »

Lizards? Turtles? No. (http://www.jstor.org/stable/2411165)
I'd look to fruit flies.

danh
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Re: Speciation of Introduced Herps

Post by danh »

Examples of this happening do exist, but you're looking at introductions very very long ago. The "native" rats of New Zealand were introduced by colonizing Polynesians and have since evolved into their own species. Herps generally have much longer generational cycles so it likely takes longer for selection pressure to shift a population, especially enough for a new species to appear. I don't know of any specific examples of what you're talking about in reptiles.

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Cole Grover
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Re: Speciation of Introduced Herps

Post by Cole Grover »

Look into Tarentola americana, Hemidactylus mabouia, and the Hemidactylus brookii/haitianus complex. The genera all have an Old World origin, but arrived in the Americas at various times and speciated (or not) from there.

As for introductions seen in our lifetimes (or even in the past 500 years), there probably hasn't been enough time to allow selection or drift to cause much variation from the founder populations. Note, however, that there's been some interesting observations on Dendrobates auratus populations introduced into Hawaii that might be worth looking into.

-Cole

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umop apisdn
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Re: Speciation of Introduced Herps

Post by umop apisdn »

I remember having read (somewhere outside of the scientific literature) that the Florida Reef Gecko (Sphaerodactylus notatus) and Florida Bark Anole (Anolis distichus ?floridanus?) are of debatable origin. I have not looked into either case very deeply myself, but I believe that the Florida Reef Gecko probably hitched a ride up at some point long ago, not necessarily of any human origin. If memory serves me right, I believe that the Florida Bark Anole has the more debatable origin, accepted as an established exotic species, but unknown whether it has truly been isolated long to have gone through the necessary process of speciation to be considered a true subspecies. It was described as a subspecies in the 40s, I am unsure of the current taxonomic status (whether truly recognized as Anolis distichus floridanus or some other subspecies), or how long it has really been present in Florida, which would play a big role in determining whether or not speciation has occurred through drift, mutations, selection, or any other route.

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Matt J
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Re: Speciation of Introduced Herps

Post by Matt J »

There's no doubt that some species can express differences in life history traits rapidly after being exposed to a new environment. I remembered this Italian Wall Lizard example from somewhere but I could only scrounge up this NatGeo article. Since differences in these traits can be induced by the environment or genetically, the next step (which they've likely taken or are currently doing) is to conduct a common garden experiment. I would put all my money on a combination of genetic and environmental. David Reznick has done remarkable work with guppies in Trinidad looking at rapid life history evolution too.

As far as rapid speciation, only time will tell :crazyeyes: :crazyeyes: (I wanted a "whooooo" emoticon but this was the closest I could find, so use your imagination)

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FunkyRes
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Re: Speciation of Introduced Herps

Post by FunkyRes »

I read a book by a Dr. Ledyard G. Stebbins. No idea if he is related to "our" Stebbins or not, but he seems to have been a leader in evolutionary biology in his day.

Anyhoo, one thing in that book (I need to find it again and buy it) was the best definition from my point of view of what actually constitutes evolution. It was something along the lines of -

If a population has adapted to new conditions in such a way that it would need to adapt to former conditions in a new way (opposed to natural selection reversion), the population has evolved.

Now, I don't think new conditions necessarily need to exist for evolution to continue, and I do think it is possible for a species to meet that definition without actual speciation, but I think that to be a rather neat way of looking at it.

IE - when domestic pigs get loose, it doesn't take them long to revert to an undomesticated form that has distinct phenotype differences such that wild boar mating with domestic sow results in visibly distinguishable offspring. Domestic rats are apparently the same way, with it not taking too many generations for escaped rats to revert to a wild type in both look and behavior, such that the crosses back with domestic are obvious. So in those cases, the adaptations to domestic environment are not evolution by his definition (he didn't give those examples, those are mine).

-=-

The representatives of old world geckos in new world is really neat, and I'm curious about the poison dart frogs in Hawaii. While not a herp, the New Zealand rats is also a very interesting case. Undoubtedly our great great grandchildren will all be long dead long before fairly recent transplants (like Bullfrogs or RES) speciate in the various places around the world where they have been successfully introduced, so thanks for the examples of where it possibly has happened and may be happening now.

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Lizardman1988
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Re: Speciation of Introduced Herps

Post by Lizardman1988 »

The Italian Wall Lizards (Podarcis siculus) in Kansas are a distinct race unto their own, there is nothing quite like them back in their native range, both morphologically and genetically.

The brown anole (Anolis sageri) in Florida, has been there so long that it is distinct from native populations, so much so that it is considered its own subspecies.

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Matt J
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Re: Speciation of Introduced Herps

Post by Matt J »

Lizardman1988 wrote:The brown anole (Anolis sageri) in Florida, has been there so long that it is distinct from native populations, so much so that it is considered its own subspecies.
Yeah but Floridians consider every species they have to be a separate subspecies :lol:

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Lizardman1988
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Re: Speciation of Introduced Herps

Post by Lizardman1988 »

Matt J wrote:
Lizardman1988 wrote:The brown anole (Anolis sageri) in Florida, has been there so long that it is distinct from native populations, so much so that it is considered its own subspecies.
Yeah but Floridians consider every species they have to be a separate subspecies :lol:
Good point :beer:

joeysgreen
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Re: Speciation of Introduced Herps

Post by joeysgreen »

I don't have much to contritube to the examples provided (except perhaps the African Clawed Frog), but along the lines of the fruit-fly comment early in this thread, there are definate differences in generation times. Turtles would likely take the longest with animals not being reproductively active until 6-9 years of age at the very earliest. More northerly introductions would take much longer. Compare this to the 2-3 years of the bullfrog and you've already halved the time, all other things being equal. Many of these geckos are sizeable enough to mate after one year of growth in warm areas. Many chameleons are sexually active at 6 months; there's jackson's in Hawaii, perhaps they will win the speciation race?

Of course this all ignores other pressures. If there is little pushing these jackson's to change in Hawaii, then they may go on several thousand generations and still be the same, while those RES in California have become a new Western subspecies.

Ian

[edit] another thought on this. When captive populations become closed off due to import/export laws, or wild populations becoming overly scarce that collection stops contributing to the captive gene pool, will we see the same speciation?

Paul White
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Re: Speciation of Introduced Herps

Post by Paul White »

I've actually kind of wondered th at, but I don't know that captive reproduction has been going on long enough in isolation from imports to really tell.But I'd love to compare a sample of a few hundred 20th generation CBB corns to a few hundred WC corns and see what differences show up.

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FunkyRes
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Re: Speciation of Introduced Herps

Post by FunkyRes »

I don't know if it is development of new genes or selection from existing genes, but I believe we have already seen changes in pyro's and GBK's - specifically the young of captive bred lines are far more likely to take unscented pinks out of the egg than young of wild caught stock.

When I crossed a WC Cal King from Redding with a multi generation CBB female, the young refused pinks but would gobble down sceloporus. A different clutch fathered by a WC Cal King from Antioch, same female, took pinks right out of the egg - many before first shed. Not enough controls or statistical significance to make a solid claim, but the anecdotal evidence anyway is that genetics play a role in what the neonates accept as food.

It only took 3 or 4 feedings of sceloporus before the lizard feeders started taking pinks.

Paul White
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Re: Speciation of Introduced Herps

Post by Paul White »

and I know ball pythons aren't regarded as really problematic feeders anymore now that they've been CBB for generations but I don't know how much of that is better husbandry vs any artifical selection (seriously, who holds back PITA animals as breeders?)

Mysticete
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Re: Speciation of Introduced Herps

Post by Mysticete »

I think you must be mistaken on the NZ rat...New Zealand is not considered to have any native rodents, nor is a separate species recognized for the rats that live there.

The only vertebrate example I can think of off the top of my head might be feral cats, which in Australia have been getting larger than average, probably because a lack of predators or competitors.

I.E. Domestic animals reverting to their ancestral form, I can think of only one example where this isn't the case. Usually, when dogs revert back to wild form, they revert back to a Dingo like animal, not a wolf like animal. I have heard this as a argument that at least some of this stems from dogs mostly being descended from a now extinct Asian dog. Interesting none the less.

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