[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Why nomenclature is changing so much now...

> From: "James Purchase"
>"Historically taxonomists have used a combination of morphological
characteristics to determine the
> relationships between and among different things, be they plants or

What's even better is that the philosophy underlying taxonomy has changed in
the last 15 years or so.  Historically, taxonomists built groups by
enchainment, where something gets put in a particular group because is has a
resemblance to a species already in that group, but not necessarily
similarity to ALL members of the group. At any rate, the approach was based
on similarity.

Currently, the entire taxonomic structure is being reworked with a different
idea in mind:  to have taxonomy reflect common ancestry.  In the new view,
groups will be groups because they all share a common ancestor and they
represent ALL the extant descendents of that common ancestry.  Now, since
relatives tend to be similar often these two approaches get you similar
grouping, but occasionally they are radically and spectacularly different.
The saxifrage family (Saxifragaceae), for example, looks like it includes
descendents from no less than six very different lineages spread widely
around the tree of the flowering plants, so it looks like the entire family
may vanish as these groups get reassigned to these other families to which
they more properly belong in the relatedness based view.  Also, other
families turn out to be simply the northern temperate (often herbaceous)
offshoots of larger tropical families (often woody).  So families like the
Parsley family and the Maple family are likely to be sunk into these older
tropical families to meet the criterion that families include all the
descendents of a common ancestor and none are nested inside other ones.

It's worth noting that there's no way to do this neatly given the vagaries
of the tree of the Angiosperms, so have a little patience while we remodel!

Doug Karpa-Wilson