Keys and hairs

Mike Crisp Mike.Crisp at ANU.EDU.AU
Wed Oct 11 14:28:28 CDT 1995

>In his communication Warren Lamboy wrote:
>"...and please, let's all agree to abandon the use of vestiture or indument
>as a plant character..."

and Servando Carvajal responded:

>"... my findings had
>demostrated that in Ficus this a strong and useful character. Of this I am
>not sure what occurs with other groups of plants."

That the usefulness (or otherwise) of indumentum should depend on the group
is exactly the point.  Irrespective of Warren Lamboy's experience of the
reliability of indumentum characters, others find them useful (or not) in
their particular groups.  A priori rejection of any character type is
essentialist nonsense.  In some taxonomic groups, indumentum characters
will be strongly heritable and reliable whereas in other groups they may be
too strongly influenced by environment and/or development, and unreliable.
The indumentum types in different plant groups are not necessarily
homologous anyway.

Here is an example from my own work on the Pittosporaceae.  In the genus
Bursaria the distribution (over the plant) and density of the indumentum
has been used to diagnose several species and many subspecies.  Users have
struggled with this taxonomy, some reporting that more than one (even 3)
taxa can be found on 1 plant!  My student Lindy Cayzer has shown that these
characters are both plastic and influenced by ontogeny, and are virtually
useless for taxonomy - seemingly supporting Lamboy's contention.  However
in the same family, the _type_ of indumentum, whether simple, t-shaped,
uniseriate, etc. is diagnostic of genera and groups within genera [see
Schodde, R. (1972) A review of the family Pittosporaceae in Papuasia.
Australian Journal of Botany, Supplementary Series 3: 1-60.]

The message here is that a priori rejection (or weighting of any sort) of
characters, especially when broadly prescriptive, is dangerous.  I do not
claim this is a new suggestion - it appears in text books.

Dr. Michael D. Crisp
Senior Lecturer in Plant Systematics
Division of Botany & Zoology
Australian National University       Phone int+ 61 6 249 2882
Canberra, ACT 0200, Australia         Fax int+ 61 6 249 5573

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