Dear David,

More please, fantastic, I do understand what you are talking about !
Sorry if it's redundant but is there anything readable on the subject
ie systematics of mollucs with a "genetic" point of view for the non
genetician mollusc amateur ?

Thank you anyway !

Sophie


>  >To Dave and others-
>>          Will you please explain the terms "monophyletic,"  "polyphyletic,"
>>and so forth.  I am supposing that they refer to the ancestry of a genus or
>>other level taxon.
>>                         Thanks,
>>                                 Linda Bush
>
>
>Monophyletic: A taxon that includes all the descendants of a common
>ancestor.  Everybody agrees that this is a good kind of taxon to recognize.
>
>Polyphyletic: A taxon that includes members from different ancestors.  For
>example, limpets are polyphyletic.  There are true limpets, keyhole
>limpets, pulmonates, etc.  Everybody agress that these should not be given
>formal names.
>
>Paraphyletic: A taxon that includes some of the descendants from a common
>ancestor but not others.  For example, Archaeogastropoda includes the
>ancestors of other gastropods, so it does not include all of the
>descendants of the common ancestor.  Cladists do not like paraphyletic
>taxa.  Traditional systematists may think they are OK as long as they are
>identified as paraphyletic.
>
>If you think of an evolutionary tree, a monophyletic taxon includes an
>entire single branch.  A polyphyletic taxon includes parts of two different
>branches.  A paraphyletic taxon includes the base of a branch but not all
>the smaller branches ones that come off the main branch.
>
>COI, or cytochrome oxidase I, is a protein in mitochondria.  The sequence
>for its gene has been used in some phylogenetic studies.  Mitochondria are
>organelles within cells that produce ATP, used for energy by the cell.
>Mitochondria are descended from symbiotic bacteria and still have some of
>their own DNA.  In most sexually reproducing organisms, very few
>mitochondria occur in the sperm and these only rarely get transferred to
>offspring.  Thus, mitochondria are almost entirely inherited from the
>mother.  You may have heard of the mitochondrial Eve in humans.  However,
>many bivalves have mitochondria passed along from fathers to male
>offspring.  This has been documented in mytilids and in unionoids.  There
>are thus sometimes two different lineages of mitochondria in one
>individual.  Molecular studies can then get confused by comparing different
>lineages of mitochondria.
>
>Thanks for pointing out the need for defintions.  Any other terms needing
>defined?
>
>PS-the computer with the signature file is working again, in case anyone
>has been wondering about the variation.
>
>
>Dr. David Campbell
>"Old Seashells"
>Department of Geological Sciences
>CB 3315 Mitchell Hall
>University of North Carolina at Chapel Hill
>Chapel Hill NC 27599-3315 USA
>[log in to unmask], 919-962-0685, FAX 919-966-4519
>
>"He had discovered an unknown bivalve, forming a new genus"-E. A. Poe, The
>Gold Bug

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Sophie Valtat
16, rue des Ecoles - 75005 Paris - France