[Taxacom] Biodiversity and paraphyly

[pierre deleporte]

As an echo to Kirk Fitzhuh's comment (under "Bar Code"), this post of 
Richard Zander (see below) illustrates quite well the fact that some 
explicit definition of "species" - and I would add, also some explicit 
notion of evolutionary processes at work - is required for allowing 
rational discusion in such 'biodiversity' and species identification matters.

Without a sufficiently developed notion of "species" and "speciation", 
nobody can usefully argue about the interest of "DNA bar code" for 
contributing to species definition or, subsequently, species identification 
- and this vails for any possible kind of "species"

Remembers me of a post by Roger Hyam on Sat, 1 Feb 2003:

>(...) The DNA taxonomy arguments raised recently have been exercised to death
>over the past few years both on this list and in the published literature.
>
>(...)
>I presume the goal of taxonomy/systematics is to produce a set of units
>arranged into some form of system that we can all agree on that reflects
>something or is useful for something. How/Why/What we do is an
>intellectual question not a technological one. You can throw as much
>data at it as you like you won't find and answer. You have to think
>about it.
>
>If taxonomy is backward it is in its conceptual approach not in the
>technology it uses.
>
>The answer you would get if you sequenced everything and gave it to an
>infinitely powerful computer is, of course, 42. Trouble is we are too
>lazy to work out what the question really is. Perhaps, if we did, people
>would be more likely to fund us to answer it.


Best,
Pierre


A 11:29 20/02/2007 -0600, Richard Zander wrote:

>  This is total nonsense. Surviving ancestors continue to accumulate
>neutral genes yet retain essential identity (phenotype and niche . . .
>remember niche?). Insisting on paraphyly in a molecular tree forces the
>splitting of species into populations (nuclear genes) or even
>individuals (mitochondrial and chloroplast genes), all of which may then
>be termed "cryptic species" and named as new species (or genera or
>families). This is what comes of abandoning the "modification" in
>"descent with modification."
>
>If a phylogenetically complex (isolated populations) species were to pup
>a new species (different phenotype and niche) from somewhere central,
>the sister group would have to be named a species, and a bunch of the
>branches lower in the tree must also. The patristic distance, measured
>as numbers of neutral base changes in DNA, between two end members among
>the populations of the species could (and probably would) be greater
>than the patristic distance between the new species and the nearest
>population of the ancestral species. When doing biodiversity triage,
>would one choose to protect the two end members of the original species
>(same phenotype and niche) because they are "genetically distant"
>(through neutral mutations) and let the new species go? Or, better,
>recognize the adaptation and fitness of the phenome in a particular
>environment as more important for biodiversity than the neutrally
>evolving genome?
>
>Biodiversity investigated with molecular analysis alone is rendered a
>mere game by excessive atomization due to focus on neutral evolution and
>forced monophyly. Eventually, with enough exemplars and exploration of
>fan-shaped pedigree charts (matrilineally inherited traits), all
>individuals will be named, or perhaps we can just stop with the
>panmictic deme in those cases when lack of resolution from mitochondria
>and chloroplasts requires studying recombining traits from nuclear
>genes.
>
>I foresee a paradigm shift back to biosystematics and the Modern
>Synthesis. Molecular analysis does not protect biodiversity. Taxonomic
>recognition of a unique phenotype interacting with a particular range of
>environmental variables with a particular reproductive system, in
>combination, does.
>
>
>Richard H. Zander

Pierre Deleporte
CNRS UMR 6552 - Station Biologique de Paimpont
F-35380 Paimpont   FRANCE
Téléphone : 02 99 61 81 63
Télécopie : 02 99 61 81 88