In the case of Phylogeny, we consider all the taxa as OTU. So, how can we interpret the various rank below species level? Or Just morphological data can provide distinction below species rank?
I think a subspecies is also a variety (but not every variety is a subspecies). Morphologists decide for subspecies and, I have heard some of them think that subspecies are unnecessary in systematics. Of course there is a relationship between the level of molecular and morphological divergence, and taxonomic rank. Some would say that species are entities that remain discrete in sympatry. If there are good references of such sympatric species in the group one is studying, one can try to extrapolate...
Dear Dr. Strelkov,
Thank you for the explanation.
Another doubt is:
What if morphologically, a taxon is considered subspecies/ variety under a species. But phylogenetically, it (subspecies/ variety) appears to be a basal taxon of the species?
Difficult question to answer. If the species concept is complex and there is no general agreement among taxonomists, the subspecies concept is even less so.
@ Dr. Carrasco,
Exactly, and if such disagreements are there at the morphology level, then it's more difficult to conclude anything at the molecular level without morphological support.
Satish, I am not good at phylogenetics. In my opinion, what matters is that they identify your basal group as a taxon, and the fact that they define it as a variety not species is their problem...
This is an interesting question. I think that DNA sequencing reveals variations more subtle than subspecies identified by morphology. In contemporary systematics you often see phylogenetic trees that indicate genetic differences within groups that reveal previously unrecognized distinct lineages, but they never use the term subspecies or variety, because in systematics every end point is technically a "species". The ultimate absurdity in this is the work being done in dogs where they try to use breeds as the end point. This is absurd, but they manage to get their stuff published in Science and Nature. I suspect that most "subspecies" would be identified as "species" and considered distinct evolutionary units as long as they can be consistently identified using DNA sequencing.
Hello Satish; The assignment of rank is a frustrating matter of professional judgement. As you follow the taxonomic literature it is evident that the professionals don't agree and it is also apparent that the definitions vary among taxa. Best regards, Jim Des Lauriers
Phylogeny can tell us about species, subspecies,but not on variety.
Why?.For example one species can has differents colours,but it has same morphologicals caracters than other specimens,so anatomy characters have more value and weight.
Morphlogicals caracters and molecular studies lets us to know if that data are correlationed and let us to built a morphological tree through genus,families,orders and so on to finished a phylogeny of species or families,etc.
@ Satish, what wonderful answers, some short and terse, to such an interesting but rather perplexing question, for which there is no definite answer, but the one from Luis Costa beats them all - i.e. an integrative approach is best. Being a traditional taxonomist myself, not having done any gene sequencing on my own, I regard small morphological variations in a sympatric population as a variety and such variations in allopatric populations as subspecies. I know that the term 'small' is arbitrary and subjective. While there are statistical methods to determine the degree of variations, bear in mind, these are also subjective. As all major taxa above the species level, are also arbitrary, all species in which reproductive isolation cannot be determined or is not present, are also arbitrary units. I take the old Darwinian approach which says that in order to determine whether one is dealing with a variety, subspecies or species should be left to the specialist concerned. If, within a sympatric population, there is a clinal variation one can refer to these variants as subspecies in the process of speciating, rather than varieties, although they may be difficult to distinguish in the overlap zone. If OTU's resulting from genetic analyses are referred to as species may be less subjective then that's the way to go but remember that when doing taxonomic studies one does not always have good material for gene sequencing and that's where the problem lies.
- Badges
- Science topic
- Similar topics
- Geoscience
- Atmospheric Sciences
- Climate Science
- Climate Change