Facilitating Rescue of Types

[Barbara Ertter]

The fundamental reason why even the most complete description cannot
replace the type is that they serve two different functions.  The type
exists to anchor the name to a set via a specified member of that set.  The
formal description is not of the type specimen per se, but of the set, and
the parameters are often compiled from numerous specimens other than the
type.  Even if only the type specimen is available at the time of
publication, the description is nevertheless intended to have predictive
value for all other members of the set, and the description is accordingly
modified in the face of new evidence as to the actual parameters.  In this
regard the components of a formal description function as falsifiable
hypotheses.
Where this dichotomy of functions is most likely to kick in is when a
species is "split", such that two sets are now recognized but the existing
description is based on the amalgamation.  Unless a description of the type
specimen per se exists independent of the amalgamated description, it is
essential that the type specimen be examined to determine which set keeps
the name, and which qualifies as a new species.

For the record, at UC-JEPS, holotypes have historically been segregated,
while isotypes are filed in the main collection, possibly the only
institution where this differential treatemnt exists.  As far as I can
determine, the rationale is derived from Alice Eastwood's dramatic rescue
of the CAS type specimens following the 1906 earthquake in San Francisco,
prior to the arrival of the flames that destroyed the rest of the
collections.  A few cabinets of holotypes we might be able to similarly
save (when the Hayward fault finally goes), whereas isotypes might be
overwhelming.  We also try to make sure that any specimens segregated from
the main sequence are cross-referenced by dummy sheets in the main sequence.

Barbara Ertter
Curator of Western North American Flora
University and Jepson Herbaria
University of California
Berkeley, CA 94720-2465  USA