Lies, Damned Lies, and DNA Barcoding

Minimalist taxonomy compromises the aims, theories, and information content of traditional systematics

“I can resist everything except temptation.” — Oscar Wilde

To say that DNA barcoding, or any form of molecular taxonomy for that matter, is the successor to centuries-old taxonomic traditions is to surrender science to technology and knowledge to expedience.  Easy grant money, prospects for employment, and the popularity that comes with following fads in biology make conforming to molecular trends a powerful temptation.  But unless taxonomists remain committed to systematics as a fundamental science concerned with the details of species diversity, diversification, and history, unless they defend its hard-won advances in theories, methods and the synthesis of multiple sources of evidence,  no one else will.  There are far-reaching consequences to allowing a fundamental science to be redefined as an applied science; to allowing information-rich revisionary taxonomy to be sidelined to expedite species determinations; and to allowing scientific names and classifications to be divorced from informative descriptions, hypotheses-based assertions of homology and synapomorphy, and the history of diversification of species and suites of characters.  It deprives taxonomy of information content, scientific understanding, and intellectual rewards.

Ekstraksjon av arvestoff (DNA) fra julemat på molekylærlaboratoriet ved NTNU Vitenskapsmuseet [DNA extraction from traditional Norwegian Christmas food at the molecular systematic lab at NTNU University Museum]. Foto: Åge Hojem, NTNU Vitenskapsmuseet [Åge Hojem, Norwegian University of Science and Technology (NTNU) University Museum]. CC BY 2.0 DEED.

Using outlines on a map, and relative positions on the globe, it is possible to identify nations, call them by name, and know their spatial relationships to one another—but to what end?  It tells us nothing of the peoples, culture, flora or fauna, languages, economic productivity, mineral deposits, or physiographic features within their borders; just names and bare minimum information.  To call an activity limited to simply telling nations apart ‘geography’ is an insult to geographers and historians who seek to understand the complexities of our world, the interactions of human populations with the land, and the sequence of events by which currently existing nations came to be.  We may be able to tell countries apart and know their names, but that stifles curiosity, undermines our understanding of the world, and diminishes our intellectual lives.  This is, by analogy, exactly what molecular taxonomy offers in the place of traditional taxonomic knowledge of the attributes of species and history of transformations by which they, and their panoply of characters, came to be.

Given the rate of species extinction and environmental degradation, there is enormous temptation to cut corners and meet immediate calls to recognize species by turning to a rapid, cheap alternative.  While the urgency of this need to identify species cannot be minimized and must be a concern for us all, it need not be used as an excuse to gut the science of systematics or limit what we ultimately know of the diversity and history of life on earth.  As important as it is that ecologists and conservatists be empowered to tell species apart, this is not our only pressing need.  As the biodiversity crisis progresses, we are in danger of forever limiting our understanding of the origins of our humanness, the diversity of earth life, and the biosphere of the world which we hope to keep in working order.  Science is just one of many manifestations of our innate urge to understand ourselves and our world, a driving curiosity that justifies our own specific epithet sapiens;  to forsake science, to settle for minimal information when we can have deep knowledge, to forego exploring biodiversity before it is decimated, are among the most unwise actions imaginable.  Expedient species identification must not be permitted to derail a two-thousand-year scientific mission to explore and know species, their characters, and their origins.  Make no mistake: ecology and conservation deserve our full support, but taxonomy deserves it, too, and has no less at stake during this period of mass extinction.  The good news is that the more we pursue our fundamental curiosity through systematics, the more, and more reliable, information we create to support ecology and conservation.  Everyone is better served by a vibrant taxonomic community and a taxonomy that does not yield excellence to expediency.

If every species looked morphologically identical, then a molecular-based taxonomy would make perfect sense.  But the vast majority do not and it is first and foremost the shockingly diverse, amazingly complex, and fantastically improbable characters of species that makes their study so fascinating and intellectually rewarding.  Early humans likely sat around a fire at night contemplating the meaning of stars in the sky, and explored their habitat by day asking similar questions about the significance of kaleidoscopic differences and similarities among the kinds of plants and animals they encountered.  Taxonomy’s intellectual drive is the same as that of other fundamental sciences, and no less strong or significant.  It is the defining feature of our own species to seek out knowledge which gave rise to physics, astronomy, chemistry… and taxonomy.  Unlike other fields, the evidence for advancing understanding in taxonomy has a sell-by date.  Regardless of how many species are ultimately conserved, it is clear that millions will go extinct and unless taxonomists remain true to their own agenda—which includes comparative and descriptive studies, phylogenetic analyses and classifications, and the assembly of synoptic museum collections of specimens—there will be major, irreparable gaps in our understanding of biodiversity and evolutionary history. 

Revisionary taxonomy may not be immediately necessary to meet our physiological needs for survival, but it is profoundly important to our continued scientific development as the dominant species shaping our planet’s future.  Homo sapiens does not live by bread alone.  We owe it to ourselves, to our intellectual lives, to the foundation of knowledge on which we base decisions and policies, to learn as much about species and their properties and history as we possibly can, while we can.  After the mass extinction, already underway, there will be no do-overs, no second chances to fill chasms in our knowledge, no other avenue by which to better understand why we and the living world are as they are.  Ecology and conservation will assure that we can survive on a radically changed planet, but taxonomy, by feeding our minds as well as stomachs, will fulfill our innate yearnings to know self and world and make surviving species known, recognizable and accessible to humankind for a vast array of purposes from agriculture to biomimicry and enjoyment.  Only by an inventory of species, and the mix of characters that make each unique, can we come to truly appreciate what we are in the process of losing, influence which and how many species survive, and assure that our future is not one of irreversible, profound ignorance.

The good news is that this need not be an either/or choice.  Yielding to molecular systematics means surrendering early in the opening battle for knowledge when victory is within our reach.  The good news is that we can have both deep knowledge of species and cladistic history and the ability to recognize species and know their relationships so that ecologists can do their job and conservationists can develop a plan to save the greatest diversity and number of species possible.  Given that we can have both, why would we consider, even for a moment, trashing centuries of progress in taxonomy for the convenience of an alternative that is, by comparison, information-poor?

To yield to the temptation of DNA barcodes and a molecular taxonomy is to effectively redefine taxonomy out of existence, to replace rigorous hypotheses with genetic distances, to abandon rich theories for efficient procedures, and to unnecessarily and literally sell-out one of the most important fundamental sciences to meet immediate needs for information.  Taxonomists have a proud tradition of making species identifiable, but as a by-product of their own rigorous science—not as a simple-minded end in itself.  Identifying species, even knowing how they are related, means very little unless we know, too, the attributes of species and clades.  Names, cladograms and classifications are all tools to access knowledge.  When that knowledge is limited to molecular data, the entire enterprise becomes a mockery of itself.

Molecular data is exciting, important, and well-established in taxonomy alongside morphology, fossils, and ontogeny.  But it is only one of several sources of evidence, no more important than the others and, in certain circumstances and for important purposes, less important than others.  Systematics practiced to its highest level of excellence involves rigorous theories, testable hypotheses, and the synthesis and integration of all available relevant evidence.  It is a lie to say we must choose between the immediate needs of environmental biologists and the integrity of systematics as an independent science.  It is a damned lie to equate a molecular-based approach, such as DNA barcoding, to the science of taxonomy.  And it is a travesty to give into the temptation of molecular shortcuts at the cost of never fully exploring or understanding the diversity of life at the granularity of species, characters and clades.

There are always temptations to take an easier path, to pursue the popular rather than the excellent, to profit by selling out integrity for shortcuts, and to conform to priorities of others rather than to boldly lead.  We are facing an extinction crisis unprecedented in human history and we are being tested.  Will we opt for the convenience, profitability, and ‘atta-boy’ approvals of colleagues, conforming to fashion and taking the low road, or will we rise to the occasion as the last generation with the chance fulfill the centuries-old vision of taxonomy to explore, know and understand the diversity and history of life?  Will we defend the integrity of systematics, build on its fantastic advances, and insist that taxonomy is done to its highest possible standards or give into easy funding and bandwagons? 

Taxonomists must resist pressures to conform to the wants of popular experimental fields at the expense of excellence of their own science.  They must resist being bought off by peer pressure and the lure of grant money; and not confuse technology and modernity with knowledge and enduring substance.  Taxonomy must be a good partner to the rest of biology while steadfastly defending its integrity.  Unless systematics reasserts itself in its full, uncompromised, multifaceted form, it may fail both in its core mission to explore life on earth and the many communities who depend upon taxonomic knowledge to achieve their goals.