[Taxacom] Fwd: complete list of all species

[Mike Dallwitz]

Paul van Rijckevorsel wrote:

> * the type determines what the name is attached to
> * the circumscription defines the taxonomic boundaries
> * a description (or a set of descriptions) of a taxon is only possible 
> and meaningful when its circumscription is established.

In a sense, descriptions must come first. The taxonomist derives the 
circumscriptions by analyzing descriptions of lower taxa or specimens. This 
may be done in the mind, or with aids such as a computer.

However, this is irrelevant to the point I was trying to make. If others are 
to make use of the concept and the associated name, the taxon must be 
adequately, accessibly, and reproducibly described. The type is a legalistic 
concept of little or no scientific value.

> I would guess that the main reason for failing identifications would 
> be the absence of good pictorial material.

The failures are due to characters that are poorly defined and/or poorly 
communicated. Illustrations are often important, but their absence is not 
necessarily the main problem.

One problem is character 'states' that are not mutually exclusive. No matter 
how well you communicate the meaning of such 'states', they will inevitably 
lead to errors in identification.

Explanatory notes and images should be prepared, and the characters tested, 
_before_ substantial amounts of data have been recorded, not as an 
afterthought just before publication. The testing should be done by having 
several people record data for the same taxa, either by recording all the 
data again, or by doing identifications from the data. Students might 
benefit from participating in this, and volunteers might find it interesting.

Testing by identification should continue throughout the development of the 
data. Checking descriptions generated from the data is not sufficient to 
ensure reproducibility: you might be confident that the description is 
correct, but be unable to reproduce it independently, which is what is needed.

-- 
Mike Dallwitz
Contact information: http://delta-intkey.com/contact/dallwitz.htm
DELTA home page: http://delta-intkey.com