GBWhite
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And the topic raises its ugly head again!
But I find it an interesting topic to debate, so I’ll throw my thoughts into the ring.
Personally, as we are talking about herpetoculture ie: keeping and breeding pet snakes that have no research or conservation value and are not bred with the intention to be repatriated back into the wild, I don’t see any problem with it.
The genus occupies a vast distribution area and like the Morelia spilota group (and has Jamie has alluded) there are transition zones where it is impossible to identify one species (if you want to call them that) from another.
Sure some display distinct patterning but I ask the question. Other than variations in patterns, is this feature significant enough to quantify the splitting of the group in the first place?
And I’d further ask. Is colour and patterning enough to elevate what may, if anything, be just a sub- species to species level and if so why is this not adopted right across the board of Australian herps? For example look at the mass variations in the colour and patterns of Common Brown Snakes (Pseudonaja textilis), variations of colours and patterns between the Southern Blotched and Alpine Blotched Blue Tongues (Tiliqua nigrolutea), huge variation amongst Spotted Black Snakes (Pseudechis guttatus) and has been mentioned the “Bells” phase of the Lace Monitor (Varanus varius).
Some have suggested that species of Antaresia have been confirmed at species level by mitochondrial DNA analysis. I’ve done a bit of digging around over the last couple of months and can’t find any data to confirm this however I would be happy if someone can point me in that direction if data is available.
As far as recognition of the current species (subspecies) of the Morelia sp group. It’s my understanding that it is still yet to be resolved. The problem is that the International Code Zoological Nomenclature (ICZN) is open to a wide range of interpretations by taxonomists (both amateur and professional).
I’ve included a link to a paper by S A Ciavaghia and associates – “Species identification of protected carpet pythons suitable for degraded forensic samples” if your interested in having a read. From my understanding of the research the use of mitochondrial DNA analysis can determine the ancestry of a genus and/or species as well as the location of individual animals but as you will see in the extract I have provided of the ICZN Code, location/distribution alone is not considered sufficient to classify taxa as a separate species. To be raised to species level a taxon must be uniquely different from other taxa. So I believe it can be argued, “What level of difference in DNA analysis contributes to a unique difference?”
Having discussed the matter with a friend that is a geneticist, it appears to me that the problem that currently exists with using DNA analysis to attempt to identify/confirm species (I’m referring to reptiles in particular) is that it is subject to variations dependant on which gene bank the samples comes from, the type of sample used, who undertakes the analysis and how the analysis is undertaken.
I’ll add that I’m not alone in my belief the validity of molecular data used to identify or validate species is somewhat questionable and should be resolved further. The phylogeny’s margin of error would drastically reduce if there were certain standards to comply with. I think this would go a long way to improving the confidence people have in the results.
For the benefit of interested;
http://www.researchgate.net/publica...ythons_suitable_for_degraded_forensic_samples
Extract
“The position of M. bredli within M. spilota and the clustering of individuals of the
M. spilota imbricata sub-species as a separate group to the remainder of M. spilota requires some comment. Morelia bredli was recently reclassified as a separate species from M. spilota without a formal taxonomic treatment [28]. Our data suggest two possibilities for the relationship of M. bredli with M. spilota: either that M. bredli
is not sufficiently divergent to be a separate species, or that M. spilota actually comprises several species, among which two would be M. bredli and M. s. imbricata. Resolution of these issues will require extensive morphological analysis and likely nuclear gene data, neither of which is trivial for this widespread group of pythons. As an interim we hereafter use ‘‘M. spilota complex’’ to refer to M. spilota, M. bredli, and M. s. imbricata in lieu of future taxonomic resolution of the complex”.
Interpretation and application of the ICZN Code
The Code rules on issues regarding nomenclatural acts and works, and aims to “provide the maximum universality and continuity in the scientific names of animals compatible with the freedom of scientists to classify animals according to taxonomic judgments”. Due to its universality, the wording of the Code leaves considerable room for interpretation.
[h=4]APPLICATION 1.[/h]“Characters”: To be available a name must “be accompanied by a description or definition that states in words characters that are purported to differentiate the taxon”. A description in the meaning of the Code is “a statement in words of taxonomic characters of a specimen or a taxon”, and a definition is “a statement in words that purports to give those characters which, in combination uniquely distinguish a taxon”. The glossary defines the word taxon as a “taxonomic unit, whether named or not: i.e., a population, or group of populations of organisms which are usually inferred to be phylogenetically related and which have characters in common which differentiate the unit (e.g., a geographic population, a genus, a family, an order) from other such units”. This latter statement clearly excludes distribution itself as a character to differentiate taxa and that complies with article 13.1.1, since it requires characters to differentiate a “geographic population” from other such units. Many taxonomists are likely to accept a geographic population, especially an insular population, only separated from other such populations by distribution, at subspecific rank. However, the Code does not distinguish between specific and subspecific rank in its requirements (Arts. 45.1, 45.2), and therefore subspecies must also be distinguishable by characters other than by their isolated locality or distribution.
[h=4]APPLICATION 2.[/h]“Generalized statements”: Generalized statements such as “separated by distribution” or “separated by analysis of DNA” or relative statements such as “usually (but not always) has” do not constitute a character in the sense of article 13.1.1 (APP1). Analysis of DNA clearly describes a method although genomic differences are of diagnostic value, and distribution itself is not a character, as it is not intrinsic to any specimen within the taxon. Therefore, these are not attributes of an organism (see glossary for character). Moreover, strictly following the glossary definition of the word description, the Code would require that a taxon must be uniquely distinguished from other taxa and generalized statements do not imply uniqueness.
Regards,
George.
But I find it an interesting topic to debate, so I’ll throw my thoughts into the ring.
Personally, as we are talking about herpetoculture ie: keeping and breeding pet snakes that have no research or conservation value and are not bred with the intention to be repatriated back into the wild, I don’t see any problem with it.
The genus occupies a vast distribution area and like the Morelia spilota group (and has Jamie has alluded) there are transition zones where it is impossible to identify one species (if you want to call them that) from another.
Sure some display distinct patterning but I ask the question. Other than variations in patterns, is this feature significant enough to quantify the splitting of the group in the first place?
And I’d further ask. Is colour and patterning enough to elevate what may, if anything, be just a sub- species to species level and if so why is this not adopted right across the board of Australian herps? For example look at the mass variations in the colour and patterns of Common Brown Snakes (Pseudonaja textilis), variations of colours and patterns between the Southern Blotched and Alpine Blotched Blue Tongues (Tiliqua nigrolutea), huge variation amongst Spotted Black Snakes (Pseudechis guttatus) and has been mentioned the “Bells” phase of the Lace Monitor (Varanus varius).
Some have suggested that species of Antaresia have been confirmed at species level by mitochondrial DNA analysis. I’ve done a bit of digging around over the last couple of months and can’t find any data to confirm this however I would be happy if someone can point me in that direction if data is available.
As far as recognition of the current species (subspecies) of the Morelia sp group. It’s my understanding that it is still yet to be resolved. The problem is that the International Code Zoological Nomenclature (ICZN) is open to a wide range of interpretations by taxonomists (both amateur and professional).
I’ve included a link to a paper by S A Ciavaghia and associates – “Species identification of protected carpet pythons suitable for degraded forensic samples” if your interested in having a read. From my understanding of the research the use of mitochondrial DNA analysis can determine the ancestry of a genus and/or species as well as the location of individual animals but as you will see in the extract I have provided of the ICZN Code, location/distribution alone is not considered sufficient to classify taxa as a separate species. To be raised to species level a taxon must be uniquely different from other taxa. So I believe it can be argued, “What level of difference in DNA analysis contributes to a unique difference?”
Having discussed the matter with a friend that is a geneticist, it appears to me that the problem that currently exists with using DNA analysis to attempt to identify/confirm species (I’m referring to reptiles in particular) is that it is subject to variations dependant on which gene bank the samples comes from, the type of sample used, who undertakes the analysis and how the analysis is undertaken.
I’ll add that I’m not alone in my belief the validity of molecular data used to identify or validate species is somewhat questionable and should be resolved further. The phylogeny’s margin of error would drastically reduce if there were certain standards to comply with. I think this would go a long way to improving the confidence people have in the results.
For the benefit of interested;
http://www.researchgate.net/publica...ythons_suitable_for_degraded_forensic_samples
Extract
“The position of M. bredli within M. spilota and the clustering of individuals of the
M. spilota imbricata sub-species as a separate group to the remainder of M. spilota requires some comment. Morelia bredli was recently reclassified as a separate species from M. spilota without a formal taxonomic treatment [28]. Our data suggest two possibilities for the relationship of M. bredli with M. spilota: either that M. bredli
is not sufficiently divergent to be a separate species, or that M. spilota actually comprises several species, among which two would be M. bredli and M. s. imbricata. Resolution of these issues will require extensive morphological analysis and likely nuclear gene data, neither of which is trivial for this widespread group of pythons. As an interim we hereafter use ‘‘M. spilota complex’’ to refer to M. spilota, M. bredli, and M. s. imbricata in lieu of future taxonomic resolution of the complex”.
Interpretation and application of the ICZN Code
The Code rules on issues regarding nomenclatural acts and works, and aims to “provide the maximum universality and continuity in the scientific names of animals compatible with the freedom of scientists to classify animals according to taxonomic judgments”. Due to its universality, the wording of the Code leaves considerable room for interpretation.
[h=4]APPLICATION 1.[/h]“Characters”: To be available a name must “be accompanied by a description or definition that states in words characters that are purported to differentiate the taxon”. A description in the meaning of the Code is “a statement in words of taxonomic characters of a specimen or a taxon”, and a definition is “a statement in words that purports to give those characters which, in combination uniquely distinguish a taxon”. The glossary defines the word taxon as a “taxonomic unit, whether named or not: i.e., a population, or group of populations of organisms which are usually inferred to be phylogenetically related and which have characters in common which differentiate the unit (e.g., a geographic population, a genus, a family, an order) from other such units”. This latter statement clearly excludes distribution itself as a character to differentiate taxa and that complies with article 13.1.1, since it requires characters to differentiate a “geographic population” from other such units. Many taxonomists are likely to accept a geographic population, especially an insular population, only separated from other such populations by distribution, at subspecific rank. However, the Code does not distinguish between specific and subspecific rank in its requirements (Arts. 45.1, 45.2), and therefore subspecies must also be distinguishable by characters other than by their isolated locality or distribution.
[h=4]APPLICATION 2.[/h]“Generalized statements”: Generalized statements such as “separated by distribution” or “separated by analysis of DNA” or relative statements such as “usually (but not always) has” do not constitute a character in the sense of article 13.1.1 (APP1). Analysis of DNA clearly describes a method although genomic differences are of diagnostic value, and distribution itself is not a character, as it is not intrinsic to any specimen within the taxon. Therefore, these are not attributes of an organism (see glossary for character). Moreover, strictly following the glossary definition of the word description, the Code would require that a taxon must be uniquely distinguished from other taxa and generalized statements do not imply uniqueness.
Regards,
George.
.....................Ron
