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Monday, February 17

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Chasing new species

I spend a large proportion of my scientific career tracking down and formally naming species that are new to science. I’ll admit that this is fun and rewarding, and that I feel a personal kinship with every amphibian or reptile that I have named. Personal feelings aside, I feel strongly that this is an endeavor—whether one works on bacteria, fungi, insects, or vertebrates—that is central to our understanding of the planet and central to our efforts to conserve our increasingly threatened biodiversity. I recently read an insightful essay by Jonathan Kennedy and Jon Fjeldsa in the journal Science that made the point “A global inventory of species diversity is critical for understanding the evolution of life on Earth.” The authors go on to say:

“Knowing how many species are present on Earth remains a fundamental scientific question whose answer is essential to generating a reliable benchmark from which current and future biodiversity losses can be gauged. Currently, as much as 86% of the world’s overall species diversity is undescribed.”

Most of my taxonomic work has focused on amphibians. The processes of cataloging, describing, and naming species and groups of species are known as the science of taxonomy. The closely related field of systematics seeks to understand the evolutionary relationships among all species. So, let’s consider some of what’s involved in such efforts. Scientists currently recognize 8,112 species of amphibians (www.amphibiaweb.org; 22 January 2020) in the world; that number was only about 6500 in 2009, so we have been busy! Of these, about 740 are salamanders, about 215 are caecilians, and the remaining thousands represent the vast diversity of frogs. However, nearly every new trip into the yet under-explored regions of the planet results in the discovery of more previously unknown species. Likewise, careful review of even well-known species reveals that they sometimes represent multiple yet-unrecognized species. I’ve got my eyes on such a well-known toad in Mexico that, I suspect, is actually two distinct species masquerading under a single name. Taxonomy is a never-ending endeavor to accomplish what seems so simple in concept: each species on Earth should have one, and only one, distinct name. Even in groups so well studied as birds, we still have a long way to go. Indeed, as we are battling to prevent the extinction of many amphibians, we are continuing to discover new species every year. This means, of course, that as the amphibian extinction crisis continues, we doubtlessly are losing species that we never knew existed. This is a point also made my authors Kennedy and Fjeldsa.

What’s in a Name?
In theory, taxonomy is a simple process based on the simple rule “A single name for each species.” Of course, nature can be tricky and consistent application of such a simple rule is sometimes quite difficult. The rules governing names, framed by the International Code of Zoological Nomenclature (ICZN) are notoriously confusing, ambiguous, and conflicting—and they often are misinterpreted and incorrectly implemented, even by experienced taxonomists!

Genus & species: Taxonomists use a system of binomial (two names) nomenclature to identify each unique species (the “species” name) and the category of genus to help identify its evolutionary relationships with other species. These names are usually derived from Latin or Greek, but words from other languages may be used. Using the scientific name for the green treefrog as an example, the first word in the binomial is the genus and is always capitalized (Hyla cinerea). The second word in the binomial is the specific epithet is not capitalized (Hyla cinerea). A species name will always be used for a given species, unless further research indicates that species is not, in fact, different from other previously described species. In this case, the invalid name is synonymized and effectively retired from use. Alternatively, an old name published even over a century ago can be resurrected if new analyses discover it to be valid. Such name changes sometimes annoy biologists and hobbyists, as the name of their focal creatures keeps changing! However, this is a necessary evil that reflects progress in our understanding of evolutionary history. Sometimes, when a species is transferred to another genus, the gender of the specific name must be changed to match that of the new genus, thus we can see subtle changes such as the case of the cane toad, which changed from masculine (Bufo marinus) to feminine (Rhinella marina) to reflect the gender of its current generic allocation. Such a change reflects the rules of Latin grammar and does not have any biological significance.

Recent common practice requires that authors include an etymology section in their paper that explains what the new name means, how they constructed it, and why they chose that name. Frequently, these can be the most interesting aspects of an entire paper (well, maybe beyond the illustrations of the new species). In previous generations, etymologies were rarely included, leaving modern scientists to guess why a particular name was chosen. In some cases, the name choice may seem obvious and appropriate — one can assume to understand why Shaw chose the name maculatum (meaning spotted) for the common spotted salamander (Ambystoma maculatum). However, one can only wonder why Carolus Linnaeus, in 1758, chose to name the cane toad Rhinella marina, apparently referring to the ocean; it is well known now that cane toads don’t live in saltwater.

Although ICZN rules allow any word (from any language) to be used as a species name, in most cases, species names are formed from Greek words, Latin words, or “Latinized” words. Several dictionaries provide word roots and combinations (e.g., Borror’s Dictionary of Word Roots and Combining Forms; Mayfield Publishing Company) that are quite useful when forming a new name or simply “translating” the names of one’s favorite creatures. Some commonly used themes and constructions include:

Geography: Geographic names often are used as a basis for forming a new name, and frequently are constructed using the suffix –ensis, which denotes place, locality, or country. An example would be the familiar American alligator Alligator mississippiensis. This name implies “the Alligator from Mississippi” in this case referencing the river and not the state, which did not exist when the name was proposed in 1802. Another approach to using geographic place names simply Latinizes the place name itself in an adjectival form. For example, the name of the toad Anaxyrus mexicanus translates into “the Mexican Anaxyrus.” Other examples include the salamander, Plethodon neomexicanus (in which case the name “New Mexico” was Latinized, which is not strictly required by ICZN), or the toad familiar to most everyone in Georgia, Anaxyrus americanus. A slightly different approach uses the place name more directly, for example, torrent salamander, Rhyacotriton cascadae, from the Cascade Mountains of Washington and Oregon. A similar method does not even Latinize the place name; for example the Costa Rican toad Incilius chompipe is from a mountain called Chompipe.

Patronyms: Honoring a person or persons is another common practice. Although clearly frowned upon professionally, the IUZN does not explicitly disallow the author to name a new species in honor of him or herself. To bestow the honor of a specific patronym for a new species upon someone can be accomplished in several ways. The most usual approach is to simply Latinize their last name. I did this in honor of Jonathan A. Campbell with the description of Incilius campbelli. A Mexican frog, Sarcohyla hazelae, was named by Edward H. Taylor, one of the most prolific herpetologists of the 20th century, in honor of Hazel Roberts, who assisted with fieldwork. Note that the masculine and feminine gender of the specific names reflect the sex of Campbell and Roberts, respectively. If one wishes to honor more than one person in the same family, then a plural ending could be used, as was done in the case of Hyla wrightorum, which was named to honor Anna Allen and Albert Hazen Wright. A creative use of this construction may be found when the taxonomist forms the patronym such that it honors a group or culture, rather than a specific person or persons; Cerrophidion tzotzilorum is a montane pitviper in Mexico named in honor of the local Tzotzil Maya people. Some names reference the language or beliefs of the people living in the region where the animal occurs. For example, the rainfrog, Craugastor chac, named in reference to Chac, the mighty God of Rain in traditional Mayan culture. Taxonomists have fun bestowing such a great honor on their heroes and friends, so patronyms are quite common on taxonomic checklists for all taxa.

Characteristics of the animal or its habitat: Another commonly used approach to forming names for new species is to base it on a distinctive feature possessed by the new taxon. Salient morphological characteristics of the animal may be singled out, such as in the case of the Mexican toad, Incilius spiculatus, which has particularly spiky tubercles on the skin, or the salamander, Hydromantes platycephalus, where platy means flat and cephalus refers to the head, providing a particularly appropriate description of this flat-headed species. The characteristic may be behavioral as well, such as in the Central American Leaf Frog, Agalychnis saltator, known for its leaping proclivities, in which saltator means jumper, or our familiar local slimy salamander, for which Plethodon glutinosus is a clear reference to its famously glutinous skin secretions. Sometimes authors will look to the habitat of the species and derive a name from that, such as the cloudforest-dwelling Mexican Treefrog, Charadrahyla nephila, where nephila is derived from the Greek nephos, meaning cloud, and philia, meaning fondness; when combined, these two words allude to the cloudforest habitat to which this species is restricted. A simpler example may be found with the U.S. salamander, Eurycea aquatica, clearly named for its aquatic habits.

The ongoing efforts to catalog, and conserve, the biodiversity on Earth is important stuff. Taxonomy, deep in the realms of the scientists who do the work, can also be controversial. Taxonomists, as it turns out, can be very territorial and dogmatic about their preferred names for the creatures they study and the debates can get ferocious. But, some of my favorite moments in my career have been those moments when I realize that a new species is before me. Sometimes it happens when I’m alone in a rainforest and I first glimpse an odd frog. Sometimes it happens after months or years of examining century-old museum specimens and reams of DNA-sequence data. Regardless, there’s the moment when I think “Hmmm, what should I name this one?”

So, next time you visit us at Zoo Atlanta, take note of the (admittedly intimidating!) scientific names on our signs and see if you can figure out why some taxonomist chose those names. It can add a fun and gleefully nerdy new layer to your visit! If you see me at the Zoo, grab me and let’s look at some names together and see if we can guess that the namer was thinking.

Pictured is the leopard-bellied scrub toad, Incilius signifer. I chose the name signifer for this species because it means “marked or patterned” in Latin, and the distinctly spotted belly of this species is one of its identifying characteristics. You may recognize that our English word “sign” also derives from this Latin word. 

Literature:

Kennedy, J.D., and J. Fjeldsa. 2020. Completing Wallace’s journey. Science 367: 140–141. DOI: 10.1126/science.aba3798

Mendelson, J. R., III.  1997.  A new species of toad (Anura: Bufonidae) from Oaxaca, Mexico, with comments on the status of Bufo cavifrons and Bufo cristatus. Herpetologica 53:268–286.

Joe Mendelson
Director of Research

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