keys are horrible
josephl at CCIT.ARIZONA.EDU
Mon Sep 11 09:17:22 CDT 1995
On Sat, 9 Sep 1995, Mr Fortuner connection modem wrote:
> For example, a
> nematode subfamily was created some time back by splitting a large genus
> (Criconemoides) into a dozen genera. This taxonomic decision was justified,
> but the resulting genera are very difficult to separate from each other
> because the phylogenetic characters used for defining them are very difficult
> to observe. Using a key to the genera often results in identification failure.
> Many identificators use an old key to Criconemoides species, find the species,
> then find to what genus it now belongs.
There are, of course, those who would maintain that genera should not be
split like this unless either 1) the existing genus is polyphyletic, or
2) there are readily usable characters available for distinguishing the
genera. Genera and families are artificial groupings created for human
convenience, having no meaning in nature. We have (correctly, in my
opinion) attempted to make taxonomy reflect phylogeny, but many
taxonomists have lost sight of the historic origins of the process.
Taxonomy is an expansion of European folk taxonomy. People in
medieval Europe, like people today, lumped organisms into groups with
common characters. They then separated species using adjectives.
Botanaists merely latinized the common binomials. Thus, white oak became
"Quercus alba" and black oak became "Quercus nigra."
In the case of polyphyletic genera, I would agree with splitting
regardless of what characters are involved. But a lot of
splitting/lumping decisions have to do with the preference of the author,
not with phylogeny. For example, the decision of whether the composites
should one family with 12 tribes or one order with 12 families is exactly
the same thing phylogenetically. The decision is one of preference and
convenience. Many taxonomists will concentrate on the differences
between species and decide to split the genus on the basis of minor
differences. Well, of course there are differences between species. But
rather than splitting the genus, one could make distinctions on the genus
or section level, not affecting the name of the species. I would much prefer
this strategy whenever splitting would not improve the phylogenetic
More information about the Taxacom