SEMINAR: Wednesday, July 29, 1998, 11:00 am
Lister Hill Center (NIH BLdg 38A), 8th floor conference room

The relationship of Xyloplax among echinoderms.
Daniel Janies, American Museum of Natural History, New York

Danies Janies is a postdoc at the American Museum of Natural History,
New York and has applied for the taxonomy position. In addition to his
interest in the evolution of echinoderms, he has done work on MALIGN and
other DNA sequence alignment algorithms.  The title and abstract of
his seminar are appended below.

  Detlef

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*  Detlef Leipe, Ph.D.                                                *
*  NCBI (GenBank)                                                     *
*  National Library of Medicine                                       *
*  NIH, Building 38A, Room 8N-805      email: leipe@ncbi.nlm.nih.gov  *
*  8600 Rockville Pike                 phone: 301-435-5999            *
*  Bethesda, MD 20894, USA             Facs:  301-480-9241            *
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The relationship of Xyloplax among echinoderms.
Daniel Janies, American Museum of Natural History, New York

Recently, several new datasets for echinoderms have emerged including:
nuclear ribosomal sequences, mitochondrial genomes, and hard and soft
part morphology.  These represent exciting possibilities for
unraveling echinoderm history.  However total evidence analyses of
echinoderm evolution are in their infancy.  For most groups, except
echinoids, the taxonomic coverage of sequence data is weak.  I have
increased taxonomic sampling of nuclear ribosomal sequences for
several echinoderm lineages.  In addition I used direct optimization,
novel means of describing sequence characters and performing
phylogenetic analyses without alignment.  In direct optimization,
molecular and morphological data are analyzed in the same context.
Homology statements among nucleotide bases are affected by their
co-optimization with morphology.  Putative nucleotide homologies are
fluid rather than static as is traditional combined analyses in which
many prealigned sequences data sets are concatenated to each other and
to morphological characters.

As pointed out by Smith (1984, 1988), relationships among echinoderm
classes are confused due largely to arbitrary assignment of aberrant
forms to high taxonomic rank.  Notable among these is Xyloplax.  I
tested the validity of the 'Class Concentricycloidea' with cladistic
analyses of nucleotide sequences and morphology from many echinoderm
and hemichordate lineages.  The sensitivity of results to various
alignment parameters was assayed with tests of taxonomic and character
congruence between data partitions.  Xyloplax is consistently placed
among asteroids.  This result is stable over a wide range of analysis
parameters and demonstrates that Xyloplax is a recent asteroid rather
than a relict stem lineage of echinoderm.  Hence, the rank of Class is
an inappropriate representation of the evolutionary history of the
concentricycloids.