This piece from Wired Science, “The mass extinction of scientists who study species.” came out a while back, but I was thinking about this problem last night. The genus Drosophila (“fruit flies” or “vinegar flies”), on which I work, has been the most important group of organisms for the study of evolutionary genetics. Indeed, much of the early advances in genetics proper, like the finding of genes on sex chromosomes, or the discovery of the linear order of genes on chromosomes, was made in Drosophila.
But all the work on evolutionary genetics of Drosophila—work on speciation, on patterns of evolution, on ecological genetics, on evolutionary biogeography, and even on molecular evolution—depends on an accurate classification of species in the group. How can you study how speciation works if you don’t know which species are the most closely related? How can you study the rates of molecular evolution unless you know how species fit into a family tree? Taxonomy—the science of classifying organisms and arranging them in their proper evolutionary relationships—is fundamental in nearly all areas of evolutionary biology. My most cited paper, published in 1989 with my student Allen Orr, critically depended on knowing the correct “family tree” of many Drosophila species.
And yet, as the Wired article shows, taxonomy is a dying field—not just for Drosophila but for all species. There is no glory, fame, or even employment for those who want to labor away at the microscope, meticulously dissecting insect genitalia or flower structure. Part of this is due to the rise of molecular systematics—the use of DNA or molecular information to reconstruct family trees—which can derive evolutionary relationships rather quickly. But before you can sequence different species, you have to identify them as different, and that relies largely on those taxonomists with microscopes and infinite patience.
When I was in college, there were many people working on Drosophila taxonomy: a group in Texas, people here at Chicago, and workers in France. Even some of the greats, like my academic grandfather Theodosius Dobzhansky, occasionally described new species. And many famous evolutionists, like Dobzhansky and Ernst Mayr, began their careers in systematics, and were driven into evolution by the need to understand the patterns they described. Now, as far as I know, there’s only one Drosophila taxonomist left: David Grimaldi at the American Museum of Natural History. He’s a superb evolutionist and taxonomist, but he’s only one person—one person to describe a luxuriant evolutionary group that may include five thousand species. And Grimaldi studies many groups, not just Drosophila.
As the Wired piece shows, what is true for fly taxonomy is true for everything. This problem becomes more critical when we try to catalog biodiversity, for such catalogs depend not just on grinding up and sequencing a lot of individuals captured willy-nilly in nature, but the painstaking labors of those traditional taxonomists who identify the groups that need grinding. From Wired:
Many biology departments within universities no longer employ a taxonomist. The remaining positions are relegated to museums.
Why? As Sørensen [Martin Sørensen, a Danish taxonomist] explains, “The declining number of taxonomists and systematists is at least to some extent linked to the fact that your scientific production today should be measurable.” And the units of measurement are collected grant money or the impact factor of a journal paper. Taxonomy has never been considered hot, and pure taxonomic studies are rarely funded, he wrote. Departments need grant money to operate.
Science as an institution may also be partly responsible for undercutting taxonomic work. Although a crude metric fraught with several issues, we measure the impact of a scientific paper by how many times other scientific papers have cited it. Similarly, we measure the impact of scientists by counting their cumulative citations. Unfortunately, taxonomic work is rarely cited, even when it should be.
On the other hand, the brilliant biodiversity databases we have created lead to a plethora of scientific papers. The Paleobiology Database, a comprehensive online catalog of fossil species, has already generated more than 100 publications. But the requirement for using this database, like most others, is citation of the database itself, not the nearly 35,000 papers generating the original data.
The decline in taxonomists means that at some point in the future we will be unable to train new generations of taxonomists. This problem is recognized by the National Science Foundation, which in 1994 created a program to enhance taxonomic research. But while this initiative provides training, it does not create job opportunities.
All the species in the world are out there. There may be as many as fifty million of them, or even more, and that’s not counting bacteria. How many species have been identified and given scientific names? Only 1.9 million—perhaps 4% of Earth’s diversity. Among the unrecognized remainder lie millions of fascinating evolutionary tales, strange adaptations, occasions for wonder—and even cures for diseases. It’s been estimated that 70% of the new drugs introduced in America in the last 25 years derive from plants. But how do you know which plants to test if you don’t know which species are out there?
Mourning the loss of taxonomy is a useless endeavor, like writing posts on the demise of the glass Coke bottle. Taxonomy will wane, even with the stimulus of molecular data, and few people will go into biology with the aim of identifying and classifying the diversity of life. In the long run, that will severely hurt not just evolutionary biology, but biology as a whole. For just as nothing makes sense except in the light of evolution, so nothing in evolution makes sense except in the light of taxonomy.
I’ve been doing science for nigh on forty years, and won’t be around, thank Ceiling Cat, when my field transforms itself into molecular biology and DNA sequencing. But while I’m here, and mourning the demise of taxonomy, let me also thank the many taxonomists whose earlier work enabled me to do what I love: studying the origin of species in fruit flies.