In part, it is hard to find many ways to reclassify mollusks that have not
already been proposed based on morphological evidence.  However, molecular
data is beginning to challenge the current standard classification at some
higher levels.  As soon as one of the current 18S-based bivalve phylogenies
gets published, for example, Myoida should start declining in usage as an
order equivalent to Veneroida.  As suggested by some morphological studies,
it seems to be a polyphyletic assemblage of veneroids that independently
adapted to deep burrowing or boring.

Several species-level revisions have been made using molecular evidence
(sequences, isozymes, etc.).  Again, most of the options had been proposed
based on morphological evidence (except for some cases in which the
morphological difference was not great enough to make anyone suspect the
presence of multiple species), but the molecular evidence provided a test
of competing morphology-based hypotheses.


>The phylogenetic
>workers using data from 12s and 16s rDNA sequences will  get to your stuff
>eventually and
>set it right if you screwed up.

Although, as mitochondrial genes, 12S and 16S have some risk of doing
strange things, especially in bivalves.  They receive mitochondria from
both parents, but occasionally one lineage will be lost and the other will
take over.  As a result, the phylogeny of the gene may not match the
phylogeny of the organism.  Molecules cannot be blindly trusted any more
than morphology, and morphologists are less likely than molecular
biologists to not have a clue about the organism itself.

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

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919-962-0685
FAX 919-966-4519

"He had discovered an unknown bivalve, forming a new genus"-E. A. Poe, The
Gold Bug