Conflicting genetics and morphology

Donald Potts potts at BIOLOGY.UCSC.EDU
Mon May 27 17:15:34 CDT 1996

One of my graduate students has several examples of cnidarian taxa that
have long been distinquished by discrete morphological and ecological
characters. We now have genetic (allozymes and ITS sequencing) data that
show so little genetic variation that they can't be interpreted: there are
few polymorphic loci (<10%), and no fixed differences if they are
polymorphic;  and genetic distances lie well within the range commonly
attributed to intra- or inter-population variation.

Taken alone, the genetic data suggest all samples belong to a single
species; but this is belied by morphological and ecological patterns that
are consistent throughout their ranges of >1000 km. So another possibility
is that they are very recently differentiated taxa.

We are interested in examples of how other people have approached analogous
situations. In particular, are there examples of compelling reasons to
justify retention of morphological taxonomic distinctions that are not
supported genetically? The literature seems full of two other situations:
        1. genetic separation of taxa not previously recognized morphologically;
        2. synonymizing taxa that cannot be distinguished genetically.

Our examples resemble the latter case, but differ in having such high
proportions of monomorphic loci in a fairly extensive genetic data set
that there is too little variation to evaluate whether the genetic
similarities are artifacts of inadequate data or reflect real biological

We do not want to debate whether genetic data are "better" than, or should
take precedence over other data. Instead, we want our interpretations to
include all available information, and we are seeking examples of how
other conflicts between independent data sets may have been reconciled in
taxonomic situations.

We will appreciate any comments or experiences

Don Potts

*   Donald C. Potts                                                       *
*        Professor of Biology                                             *
*        Director, UCSC Education Abroad Program                          *
*                                                                         *
* A316 Earth and Marine Sciences Building                                 *
* University of California                  Phone: (408) 459-4417         *
* Santa Cruz                                Fax:   (408) 459-4882         *
* California  95064   U.S.A.                Email: potts at *

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