Termite Experts Attempt to Solve Taxonomic Cold Cases
By Richard Levine
Coptotermes is one of the most economically destructive genera of termites, and it includes the Formosan subterranean termite (Coptotermes formosanus). For years, taxonomists have struggled with a long list of described species around the world. As some species were described multiple time, species names were gradually removed from the list, which was narrowed down to just 69 valid species within the genus as of 2013. However, some termite researchers think that many names still do not represent a valid biological taxon.
Thirty-one of the world’s leading termite experts from 24 institutions around the world have formed a consensus that there is only solid evidence for 21 species. Their findings appear in the journal Systematic Entomology.
Over the past 150 years, more than 140 species of Coptotermes termites have been described. However, many were described a very long time ago and have not been seen since. Some specimens are not easily accessible, and sometimes there are no usable specimens in museum collections to study. Another problem is the fact that Coptotermes termites — even individuals of the same species — have high levels of morphological caste plasticity. That’s a fancy way of saying that they do not always look like each other. In fact, according to one of the authors, Dr. Thomas Chouvenc of the University of Florida’s Ft. Lauderdale Research and Education Center, “There is sometimes more variability within a single colony than across species,” which may have caused entomologists in the past to mistakenly think they were seeing multiple species instead of just one.
Finally, there is the possibility that two or more entomologists have described the same species without knowing it, and have assigned them two different names. This happens a lot in entomology, and taxonomists have developed a way of dealing with it by “synonymizing” the names. In other words, after verifying that the two species are indeed one and the same, they choose the name that is most valid (it is often the older one) and dub it the official scientific name, while the other name is then known as a synonym. That’s how the 140+ species of Coptotermes termites that were described over the past 150 years were reduced to just 69 species in 2013.
In order to make a formal synonymy, there’s a list of rules that must be followed. In brief, you need to have the original specimens and you need solid scientific evidence to show that species X and species Y are actually the same. However, that is impossible in many cases where specimens do not exist, are not usable, or are not accessible.
This creates a sad dilemma. Many names should be removed from the list of “valid” species within a genus, but because of the strict rules of taxonomy, it is impossible to actually do a formal synonymization. This results in hundreds (or even thousands) of what Dr. Chouvenc refers to as “taxonomic cold cases.”
So how did the researchers reduce the number of Coptotermes species from 69 to just 21?
That’s where things start to get interesting. Instead of focusing on the taxonomic rules of synonymy, the researchers decided to come up with a short list of verified, valid species.
“Because we cannot access many of the type species, and because some of the names have not been used for decades, some of these names became very suspicious, especially with the advent of molecular biology,” Dr. Chouvenc said. “Because of the rules, we cannot formally ‘kill’ a species name simply by saying ‘we think that this is just a synonym of species X.’ That is a big no-no. Instead, we came together as a community of termite experts and gathered all of the literature, personal knowledge, and opinions of all the species that we respectively work on. With such insight, it became more and more obvious that some names are synonyms of known species, but we can’t really complete a formal, case-by-case synonymization process. So we came up with a consensus that 21 names represent a given species. For all of the others, we don’t know, but chances are VERY high that they are synonyms of one of the 21 species that we think are valid.”
Following the formal taxonomic rules would be nearly impossible, so the researchers basically agreed to try to clean the mess up as best they could.
“Instead of taking the usual taxonomic approach, we gathered the opinions of the world’s experts and we came up with a short list of 21 species that should be deemed valid based on morphological and molecular evidence,” Dr. Chouvenc said. “This approach is completely improper from a taxonomic point of view, but it allowed us to come up with actual ‘functional units of species’ that are relevant to science and the biology of the genus. In other words, we’re saying that these are the species that matter, and all of the others are either bogus, synonyms, or they may be valid but no one really knows. We are being practical, and this short list is very practical.”
“Technically, the formal synonymization process remains to be completed for many of these species,” he continued. “But at least we came up with the agreement on the direction to take to achieve such a goal. This is a moving target, where some old species are synonymized and some new species are being described. We cannot be fully satisfied with this functional short list, but at least it’s a start.”
All of the 31 authors contributed to the writing, and it took more than 50 versions of the manuscript before they could come up with an acceptable consensus. When asked whether this approach could be applied to other insect groups as well, Dr. Chouvenc said, “We hope that the consortium approach could be a model for a scientific community to tackle taxonomic hard cases as a group rather than as dueling researchers. We believe that the consensus reached by the consortium may serve as a road map to provide a strong incentive to solve controversies within the Coptotermes genus in a foreseeable timeframe, and ultimately this approach could be applied to other important insect genera.”
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Richard Levine is Communications Program Manager at the Entomological Society of America and editor of the Entomology Today Blog.