SCIENCE OBSERVER
Attacks on Taxonomy
Roger Harris
Most people view taxonomy as a rather dry field of science, so when
an online auction to name a new species of Bolivian monkey brought
the science of classification to the public's attention, taxonomists
were surely delighted. Among the bidders was television celebrity
Ellen DeGeneres—who lost to the winning bid of $650,000.
But the publicity did little to unite two camps engaged in a debate
that threatens the very foundations of the nomenclatural edifice
upon which all of modern taxonomy is built. The melee, reports of
which are turning up in popular magazines, is between some
scientists who want to implement the PhyloCode, a new method of
naming taxonomic groups, and those who want to keep the existing system.
The PhyloCode would name and organize living things based on common
ancestry and the branching of the evolutionary family tree. It is
based explicitly on phylogeny, the evolutionary history of a species
or higher taxonomic group.
Its proponents mean to replace the venerable system developed by
Carl von Linné (Carolus Linnaeus, 1707-1778), the father of
modern taxonomy, in the mid-1700s and used universally by scientists
since then. Linnean classification organizes species in a
hierarchical scheme based largely on similarities in their forms and
other traits that usually, but not always, reflect evolutionary relationships.
Unlike the PhyloCode, Linnean taxonomy does not formally incorporate
phylogeny. However, its ranks (species within genus, genus within
family, family within class and so on) imply evolutionary
relationships. The main drawback of the Linnean system is that
groups must be named with suffixes that denote their rank in this
hierarchy. For instance, all animal families end in -ae, as in
Hominidae. Reclassification of an existing species or discovery of
new one can lead to changes in rank and therefore require renaming
whole suites of taxonomic groups—a cascade of
renaming—even without any new information on those groups. The
Phylo-Code solves this problem.
The core proposition of the PhyloCode is to abandon Linnean
hierarchical ranks and recognize only species and clades.
(A clade is a group of all the organisms that share a particular
common ancestor.) The scheme does not dispense with hierarchical
organization, as clades will be nested within one another according
to phylogeny. The key advantage is that changes made in one part of
a classification do not require altering other group names. The
PhyloCode's use of common ancestry to establish taxonomic
relationships—the practice called cladistics—has
received greater impetus in recent years. Molecular data enable
workers to determine relationships with greater certainty than using
physical resemblances alone.
Although the clade concept is well defined, PhyloCode workers have
not yet established rules for converting existing species names or
for naming new species; at least a dozen proposed methods are on the
table. Several involve retaining the binomial name (genus, species:
Homo sapiens) but formatting it differently to
distinguish from clade names, so that human beings might become
homosapiens in the Hominid clade.
How would this system affect naming of new species? Robert Wallace,
discoverer of the monkey whose naming rights were up for auction,
and his team used Linnean rules. If the monkey's name is changed
according to PhyloCode rules, it could end up quite different from
what the winning bidder, an as-yet-unnamed commercial enterprise,
had in mind. Perhaps callicebusmicrosoftii, or callicebuswalmartus?
Supporters say the PhyloCode is simple and will properly reflect
evolutionary connections between species, thus promoting stability
and clarity in nomenclature. Kevin de Queiroz, a research zoologist
at the National Museum of Natural History and an early architect of
the PhyloCode, says that, with the phylogenetic system, names of
taxonomic groups "will make more sense from an evolutionary perspective."
But the PhyloCode is meeting resistance. Critics say that the
Linnean system effectively organizes and conveys information about
taxonomic categories at all levels of biological organization and
that replacing this system does not justify redefining millions of
species and higher taxonomic levels. If the PhyloCode is adopted,
the change could mean reworking the names of 1.75 million species
(and counting).
According to Michael Benton, chair of vertebrate palaeontology at
the University of Bristol, the proposed changes for species names
will require systematists to redefine all the species named so far.
"This opens up endless vistas of fruitless time-wasting and
bickering," Benton says, "and for no benefit
whatsoever." He worries that the arguments will result in loss
of funding and respect for taxonomy.
De Queiroz argues that much of the protest is overblown. "The
system that we‘d like to replace is virtually unknown to the
general public," he says. "We're not talking about
replacing names; we are talking about replacing the rules governing
those names."
Even if academic, the debate has implications. Implementing
the Phylo-Code could profoundly affect global biodiversity catalogs.
One of these is the Catalogue of Life, a coordinated effort to
categorize and document all life on Earth. In March, Catalogue of
Life scientists announced they now have information for half a
million species in their database. The work continues apace. Yet
there's barely a nod to the PhyloCode in the relevant literature.
Paul Kirk, a biosystematist at CABI Bioscience, a nonprofit
life-sciences research organization collaborating on the project,
points to "friction between those who wish to represent life on
earth in a 'PhyloCode' way and those who wish to follow the
traditional Linnean hierarchy." Although the Catalogue of Life
is "firmly based in the Linnean system," the project's
participants are talking about how best to manage a possible merger
of the systems.
Frank Bisby at the University of Reading, executive director of
Species 2000, another Catalogue of Life partner, believes that
cataloging efforts can readily incorporate whatever classification
system is used by taxonomists. "We're not taking a precise
position," he says. "We're asking the specialists to keep
us up to date, and that means in one group of organisms we're using
natural [Linnean] concepts, while in others we're using the modern
[phylogenetic] systems.… There's no claim the database tree
is perfect or accurate."
Paul Kirk observed that the two systems "should be able to run
in parallel." But Benton is less sympathetic: "In
understanding biodiversity, the PhyloCode merely introduces semantic
debate; it can provide no enlightenment of real issues."
At the moment, the Linnean camp has the upper hand, with the weight
of numbers and of history. But the PhyloCode is gathering support.
Will Ellen DeGeneres get to name her monkey after
all?—Roger Harris