New article about Tylototriton verrucosus and shanjing (continued)

[JM29]

Hello.

This article may seem a bit off-topic, but it documents a case of apparent paraphyly caused by mitochondrial introgression :

Heredity 102, 590-599 (June 2009) | doi:10.1038/hdy.2009.26

• Introgression as a likely cause of mtDNA paraphyly in two allopatric skippers (Lepidoptera: Hesperiidae)mtDNA introgression in allopatric duskywings

E V Zakharov, N F Lobo, C Nowak and J J Hellmann
Abstract

Gene transfer between species during interspecific hybridization is a widely accepted reality in plants but is considered a relatively rare phenomenon among animals. Here we describe a unique case of mitochondrial DNA (mtDNA) paraphyly in the skipper genus, Erynnis, that involves well-diverged allopatric species. Using molecular evidence from both mitochondrial and nuclear genomes, we found high levels of intraspecific divergence in the mitochondrial genome within E. propertius (over 4% pair-wise sequence divergence) but no such differentiation in the nuclear genome. Sequence comparisons with related Erynnis suggest that past, but recent and infrequent introgression between E. propertius and E. horatius is the most reasonable explanation for the observed pattern of mtDNA paraphyly. This example of putative introgression highlights the complexity of mtDNA evolution and suggests that similar processes could be operating in other taxa that have not been extensively sampled. Our observations reinforce the importance of involving multiple genes with different modes of inheritance in the analysis of population history of congeneric taxa.
Heredity 102, 590-599 (June 2009) | doi:10.1038/hdy.2009.26

To come back to the two species of Tylototriton, if chinese samples were caught on a limited area, a past introgression could have happened between them. So, John is right in saying more distant verrucosus sample must be studied before making a conclusion.

Maybe mtDNA alone is not such a good criteria.

Sincerely,
JM

 

[markusA]

just to add two other possibilities for discussion:

1. mtDNA is bequeathed by the mother. as SW Yunnan is a contact zone between Tylototriton who look different (even Tylos from N Burma could be another species than Indian ones): it could be a mixed breed zone as well and verrucosus males maybe migrated to shanjing sites and produced offspring with shanjing females, that look like verrucosus. These offspring will have mtDNA from mother and can have nuclear DNA from father
(I know that there are different reproduction modes, but who knows how the Burmese Tylos "do it"? could be different from Indian ones)

2. nuclear mitochondrial insertion: Numt
parts of the mitochondrial DNA are included in nuclear DNA
this is then a problem of investigation: it can happen, that not the mtDNA is sequenced but the Numt, and if the animals derive from a common ancestor not long ago, the Numt can be very similar.
there are possibilities to avoid this, but this phenomenon is underestimated and possibly let to a bigger number of false study results in the past

The information of just a part of mtDNA cytb is limited and should not result in a taxonomical decision without further investigation of nuclear DNA and other localities.

I am ecologist and just start to learn about systematic and DNA, so maybe there are experts in the forum who can approve the above mentioned theories.

 

[JM29]

Just to add a more "caudate" view, one can read the attached file (Babik et al, 2005, on Lissotriton vulgaris and L. montandoni), and see that mitochondrial DNA is difficult to connect with usually recognised species.
An error source may comme from studying mtDNA alone. More global genetic studies would be more useful.

 

[JM29]

And yes, I fully agree with you, markusA.
mtDNA alone may not be sufficient to decide taxonomic changes.
It can help, being a criteria among others.

Sincerely,
JM