[Taxacom] Elimination of paraphyly: sensible or not?

Thu Feb 8 17:53:14 CST 2018

A paper proposing an alternative approach, recognizing paraphyletic groups,
is available at https://kuscholarworks.ku.edu/handle/1808/17551 or
http://www.bioone.org/doi/full/10.17161/PC.1808.17551

The fundamental problem of the Phylocode is that the best way to convey
phylogenetic information is through a phylogeny, and the most important
function of a system of biological nomenclature is to clearly convey what
taxon we're talking about.

In some cases, eliminating paraphyly is practical and useful.  Eliminating
polyphyly is usually desirable (although contexts exist where a
polyphyletic group is useful, such as "algae" as an ecological category).
But in other cases, eliminating paraphyly is not practical.  Replacing
familiar names with new ones for every slight change in content is not
helpful, though a strict reversion to original usage for every name would
be disastrous as well - many Linnaean genera are at best families and at
worst at least one would include most of Eukarya if it were expanded to the
smallest monophyletic group including all originally included taxa.

On Thu, Feb 8, 2018 at 5:42 PM, Neal Evenhuis <neale at bishopmuseum.org>
wrote:

> I had a similar discussion with a pattern cladist once and his response
> was “Hey, you’ve got a point …. but if you comb your hair differently, it
> won’t show.”
>
>  -Neal
>
> On Stardate 2/8/18, 12:07 PM, Star-trooper "Taxacom on behalf of Stephen
> Thorpe" <taxacom-bounces at mailman.nhm.ku.edu<mailto:taxacom-bounces@
> mailman.nhm.ku.edu> on behalf of stephen_thorpe at yahoo.co.nz<mailto:
> stephen_thorpe at yahoo.co.nz>> wrote:
>
> Hi all,
> I have been giving some thought to the cladistic obsession of eliminating
> paraphyly in taxonomic classification. For many taxa (above species), the
> subtaxa consist of one or more clearly monophyletic groups, plus a possibly
> paraphyletic residue (i.e. no apomorphies to bind the residue together into
> a monophylum). So, if we must eliminate paraphyly (or possible paraphyly),
> the only options are to either: (1) subsume the monophyletic subtaxa into
> the paraphyletic residue; or (2) break up the paraphyletic residue into
> monophyletic subtaxa. Effectively the two options may actually be
> equivalent. An example might help to illustrate my point. Let's take a
> simplistic view of reptiles as scaly tetrapods, birds as feathery winged
> bipeds derived from reptiles, and mammals as hairy tetrapods derived from
> reptiles. So, amniotes (reptiles, birds and mammals) are a monophyletic
> group, as are birds and also mammals, but not reptiles (reptiles being the
> "paraphyletic residue"). We wish to retain birds and also mammals as useful
> monophyletic taxa, for obvious reasons. So, what to do? Luckily, within
> reptiles there are some monophyletic subgroups of sufficient diversity to
> be useful, but this might not have been the case if all reptiles were just
> basically "skinks", with only species or perhaps also generic differences
> between them. Had this been so, amniotes would have to be taxonomically
> split between numerous (maybe hundreds) virtually identical taxa of
> "skinks", plus birds and also mammals as just two taxa at the same level
> (not necessarily a ranked level, but direct child taxa of amniotes). Would
> this be a useful classification of amniotes? I suggest that it would be far
> more useful to recognise a single paraphyletic taxon of reptiles (all the
> "skinks" in the hypothetical example), plus birds and also mammals (i.e.
> just 3 direct child taxa of amniotes). I wonder for plants, fungi and also
> invertebrates, if there might be many taxa analogous to the above
> hypothetical example, with a paraphyletic residue consisting of hundreds of
> "skinks", but also with just one or two very distinct and diverse
> monophyletic subtaxa? If so, would it be sensible to eliminate paraphyly or
> best just to live with a known paraphyletic residue as a unified subtaxon?
> Given the amount of limited resources which are being allocated to projects
> to eliminate paraphyly, to the detriment of alpha taxonomy, it would be
> nice to think that there was a clearly good reason for the elimination of
> paraphyly, but I'm not so sure that there is! The usual argument seems to
> be that you cannot make meaningful predictions from paraphyletic taxa, but
> how much biology does rely on the making of predictions based on taxon
> membership, and what proportion of those predictions end up being true
> anyway? For example, you might predict that a newly discovered braconid is
> a parasitoid, but a few braconids are phytophagous anyway. So, I guess that
> the main question that I am posing is whether we think that the benefits of
> monophyly justify the spending of so much limited resources on the
> elimination of paraphyly? Perhaps the elimination of paraphyly is being
> driven instead by economic factors, doing phylogenies being a more cost
> efficient way for institutional scientists to spend their time on than
> alpha taxonomy?
> Stephen
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-- 
Dr. David Campbell
Assistant Professor, Geology
Department of Natural Sciences
Box 7270
Gardner-Webb University
Boiling Springs NC 28017