Linnean naming system faces challengers
10:00 12 September 04
A band of renegade biologists is taking on a mammoth task that
threatens to upset a status quo that has been unchallenged for almost
250 years. Put simply, they want to change the way scientists name
every living organism on the planet.
These rebels say that our system of naming plants, animals, fungi and
bacteria, famously introduced by Linnaeus in 1758, is frustrating
efforts to understand the living world. They want to replace it with a
more rational scheme they call the PhyloCode.
Critics have slammed their proposal, arguing that it will be a waste of
time and effort that will hinder the urgent task of cataloguing the
thousands or even millions of as yet undiscovered species before they
go extinct. It could also compromise laws designed to protect
biodiversity, placing endangered species at unnecessary risk.
Linnaeus developed the now familiar binomial system of nomenclature, in
which the name of each species includes its genus. This identifies Homo
sapiens , for example, as a member of the genus Homo .
That system has since been expanded, so that every identified living
species is also placed in a hierarchy that stretches from phylum at the
top, down through class, order, family and genus.
For instance, the genus Homo belongs to the family Hominidae, which is
part of the order Primates, which in turn belongs to the class
Mammalia, which is a member of the phylum Chordata.
Because this scheme sorts organisms loosely into just a few
hierarchical divisions, it tells us relatively little about how they
are related in evolutionary terms. And that, advocates of the new
naming scheme say, is hindering our understanding of the natural world.
"The whole endeavour of trying to understand and communicate about the
diversity of life is being compromised by a naming system that is
outdated and has bad consequences," says Michael Donoghue, an
evolutionary biologist at Yale University.
Under the Linnaean system, a taxonomist who wishes to name a group of
organisms must also assign that group a rank, such as genus or family.
But there are not enough of these to cope with the increasingly complex
branching of the evolutionary tree now being discovered. To keep up,
taxonomists have been inventing a confusing raft of new ranks, such as
phalanxes, infracohorts and supertribes.
Even worse, biologists who identify a new group may find they have to
change the ranks - and therefore the names - of several other groups in
order to maintain some semblance of consistency.
This, Donoghue claims, discourages people from naming groups as they
are discovered, and thus limits the progress we can make in our
understanding of how different groups of animals or plants are related
to each other.
For example, Donoghue and his colleagues have recently discovered that
the genus Potentilla , which belongs in the rose family, does not form
a natural evolutionary group, technically known as a clade. A clade is
made up of an ancestral species and all its descendants; think of it as
that part of an evolutionary tree that would fall off with a single saw
One subset of Potentilla does form a clade, but other Potentilla
species arise elsewhere in the tree, while plants placed in other
genera lie on intermediate branches.
To fix the problem, taxonomists would either have to group these other
genera within Potentilla - which would mean renaming hundreds of
species, including familiar ones such as the strawberry - or restrict
the name Potentilla to members of the smaller clade and find new genus
names for the rest. Either option involves a huge amount of work
shuffling species in and out of genera.
The PhyloCode would eliminate the need for that by abolishing genera,
families and every other rank above the level of species. Instead,
taxonomists would be free to define and name any clade they discover.
Donoghue's team could assign a name to the clade they found in
Potentilla , but they would be under no obligation to name or rename
any other clades at the same time. That will allow naming to track our
understanding of biodiversity more closely, says Philip Cantino, a
botanist at Ohio University in Athens.
Cantino and Kevin de Queiroz, a lizard expert at the Smithsonian
Institution in Washington DC, have drafted a set of rules governing
PhyloCode names. At a meeting in Paris in July, PhyloCode proponents
began the task of applying this code to the Earth's living things.
The meeting will form the basis of a book to be published in two or
three years' time that will mark the official beginning of PhyloCode
names - "the way Linnaeus was the starting point for the other codes,"
as Donoghue puts it.
Though the new system will change the way taxonomists name organisms,
PhyloCoders hope that everyone else - even other biologists - will
notice little difference. Today's familiar names should still apply.
Humans, for example, would be a species called sapiens in a clade
called Homo , so we would continue to call ourselves Homo sapiens . The
only change is that the clade would no longer have the rank of genus.
As innocuous as it sounds, the idea has provoked angry protests from
Taxonomists, already thin on the ground, are frantic to catalogue as
much of the world's biodiversity as they can before it disappears.
"We're the last generation that will have access to this enormous
diversity of species, and to piddle away our time implementing a new
system is a tragic waste," says Quentin Wheeler, an insect taxonomist
at Cornell University in Ithaca, New York.
The implications are more than just academic. The machinery of
conservation, from laws like the US Endangered Species Act to
international agreements such as the Convention on International Trade
in Endangered Species, is based on the existing system of names.
"Trying to change that system of naming right now would be utter
chaos," says John Kress, a botanist at the Smithsonian Institution who
works extensively with government agencies on biodiversity issues.
Savvy traders in endangered species would be quick to exploit any
ambiguities during the changeover, says Dennis Stevenson of the New
York Botanical Garden, who serves on the cycad specialist group for the
World Conservation Union (IUCN).
Donoghue concedes that the transition may bring some uncertainties.
"The prudent thing to do is to experiment with this," he says. "Then
we'll understand the pros and cons much better and we can either modify
things or decide not to do it at all. But my guess is that once we've
done the experiment we'll end up strongly preferring the PhyloCode."
Given the hostile reception PhyloCode has received so far, they have a
lot of convincing to do.
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