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Thomson, S. A., & Cann, J. Chelodina hybrids.
Added by: Admin (14 Aug 2008 20:36:28 UTC) Last edited by: Beate Pfau (28 Dec 2009 18:03:17 UTC) |
| Resource type: Personal Communication BibTeX citation key: Thomson2003a View all bibliographic details  |
Categories: General Keywords: Chelidae, Chelodina, Chelodina canni, Chelodina georgesi, Chelodina longicollis, Chelodina novaeguineae, Chelodina reimanni, Chelodina rugosa, Elseya, Elseya novaeguineae, Schildkröten = turtles + tortoises, Systematik = taxonomy Creators: Cann, Thomson |
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| Abstract |
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In the description of Chelodina canni by Bill McCord and myself we describe a natural hybrid population of Chelodina canni and Chelodina longicollis. Chelodina canni also hybridises with Macrochelodina rugosa. There are pictures of this hybrid in John Cann's "Australian Freshwater Turtles". Oh, I know that the hybrids can breed in this species too. As we definitely had F2+ generations based on allozymes. I saw some specimens of Chelodina reimanni in the Dresden Museum a few years back that I was positive were hybrids of Chelodina reimanni and Chelodina novaeguineae, but I had no proof of this. I believe that hybrid sea turtles have been found on rare occasions, but am not sure about this one. Galapagos Tortoises frequently hybridize but this is at the sub species level, in fact over 80% of the Galaps in captivity are hybrids. Ok these are some examples but I want to make a point about hybrids too. Hybridization is considered genetic contamination by the IUCN, its therefore actually one of the lowest acts keepers can do. However, we all know it frequently occurs in animals other than turtles. Its often done to raise the value of the offspring, and is a part of the domestication process too (which also involves selective and in-breeding). Turtles keepers seem to have avoided this urge so far. Personally I consider that as a generalization animals can hybridize. However, when they can't two reasons account for it. First they have an historical overlap and have developed genetic barriers, or two they have drifted genetically to the point that they are incompatible. Probably sounds obvious but what it means is that any allopatric species, can probably hybridize and the closer they are related the greater the danger that this may occur. Hence closely related, allopatric species should not be kept together. To the poster who (tongue in cheek) commented that species are a human construct.. Yep I agree, and I am a taxonomist. However, there is considerable tested evidence now that at least the species level is real. At least when properly identified. Sub-species are generally figments of the imagination and are actually allopatric isolated breeding communities of the same species that differ for the same reasons that allopatric populations of humans differed historically. The Genus and above are also rather vague. The genus and higher levels are, loosely, a measure of how closely related two species are. Hence within genus hybridization is more common than extra-generic hybridization. New Freshwater Tortoises of Australia JOHN CANN 26 Yarra Rd., Phillip Bay, New South Wales, 2036 Australia Research into Australian freshwater turtles has greatly advanced during the last decade. Numerous new forms have been formerly described, and many papers describing turtles have been submitted or are in their final stages of preparation. This new work has been driven by extensive surveys for new forms, to which I am pleased to have contributed substantially, renewed interest in turtle taxonomy by some bright students, and the introduction of some modern molecular techniques to the problem of defining species boundaries objectively. This work has confirmed many ideas on new species, as outlined in the literature, but it has also yielded some surprises. The cryptic species pair of saw-shell turtles, Elseya georgesi, from the Bellinger and Elseya purvesi from the Manning, is one example. Three instances of hybridization among the snake-necked turtles, Chelodina provide other examples. Chelodina novaeguineae is hybridizing with Chelodina longicollis where their ranges meet in central Queensland, and C. novaeguineae is hybridizing with C. rugosa in the Gulf country, despite their distant relationship. Back-crossed individuals have been found, providing a real challenge to our ideas of what a Chelodina species is. Whatever the final figure is for the number of Australian freshwater turtle species, this critical information is coming to light at a time when many populations of turtle are in decline as human and aquatic wildlife populations compete for a very limited resource in Australia - water. This fundamental taxonomic work is critical if we are to balance conservation concerns with development.
Added by: Admin Last edited by: Beate Pfau |