In a biological sense, large scale hybridization at the population level is
termed reticulate evolution. It is reportedly common in some scleractinian
coral phylogenies, modern African cichlid fishes and some plant groups such
as oaks (see Veron 1996; Sylvester-Bradley 1977). I know of no reports of it
within the mollusks. At a lower scale, hybridization occurs among
individuals within different species populations, for example within
vertebrate groups such as the white-tailed and mule deer of North America
and also is some warbler groups, etc., but it occurs infrequently enough
that the species remain distinct. I am not sure of the scale your question
addresses.

From a cladistic analysis point of view, hybridization at the reticulate
evolution scale is problematic since members of two presumably monophyletic
groups fuse to form a third group which may then be monophyletic afterwards.
It is a struggle with which I am currently dealing. Computer based character
analysis programs such as PAUP have no way to address whether or not a
reticulate event is more parsimonious. If anyone out there has any ideas on
how to address this issue, I would welcome them.

Lee Spencer

Veron, J. E. N. 1996. Evolution in corals, IN George D. Stanley, ed.
Paleobiology and biology of corals, The Paleontological Society Papers,
1:7-37. (ISSN 1089-3326)

Sylvester-Bradley, P. C. 1977. Biostratigraphical tests of evolutionary
theory, IN Erle G. Kauffman and Joseph E. Hazel, eds. Concepts and Methods
of Biostratigraphy, Dowden, Hutchinson & Ross, Stroudsburg, Penn. (ISBN
0879332468)



-----Original Message-----
From: Conchologists List [mailto:[log in to unmask]] On Behalf Of Andy
Rindsberg
Sent: Thursday, June 30, 2005 9:43 AM
To: [log in to unmask]
Subject: Re: hybrids

Art and Olivier,

Hybrids have no status under the International Code of Zoological
Nomenclature (http://www.iczn.org/iczn/index.jsp), but the International
Code of Botanical Nomenclature does accommodate them. Here are the relevant
parts of the ICZN:

Article 17. Names found to denote more than one taxon, or taxa of hybrid
origin, or based on parts or stages of animals or on unusual specimens. The
availability of a name is not affected even if

17.1. it is found that the original description or name-bearing type
specimen(s) relates to more than one taxon, or to parts of animals belonging
to more than one taxon; or

17.2. it is applied to a taxon known, or later found, to be of hybrid origin
(see also Article 23.8); or

17.3. it is based on only part of an animal, or one sex, or one stage in the
life cycle, or one of several dissimilar generations, or one morph or caste
of a polymorphic species, or a parthenogenetic form, or a specimen which is
an unusual example of the taxon (for exclusions see Articles 1.3 and 45.6).

23.8. Application to species-group names established on hybrids. A
species-group name established for an animal later found to be a hybrid
[Art. 17] must not be used as the valid name for either of the parental
species, even if it is older than all other available names for them. Such a
name may enter into homonymy. For names based on taxa which are of hybrid
origin see Article 17.2.

What all of this says is, "Don't give animal hybrids a new species name. If
one is named accidentally, then stop using the name and don't use the same
spelling for anything else in the future. But if an author takes a name
based on a nonhybrid type and applies it to a hybrid, the name is still
valid for the original, nonhybrid species."

The rules for plants are quite different, but someone else will have to
explain them.

(Aside to Art: Hope you're doing well in the city of Sus alatus. If you have
a hankering for sauerbraten, I highly recommend Ron's Roost in the Western
Hills; they still ferment their beef the old-fashioned way.)

All the best,
Andy

Andrew K. Rindsberg

----------------------------------------------------------------------
[log in to unmask] - a forum for informal discussions on molluscs
To leave this list, click on the following web link:
http://listserv.uga.edu/cgi-bin/wa?SUBED1=conch-l&A=1
Type your email address and name in the appropriate box and
click leave the list.
----------------------------------------------------------------------