Pygmy grasshoppers come in many shapes and colors and are often exciting to see, but their taxonomy is a mess.
Guest blog post by Josip Skejo & Niko Kasalo
A lovable mess
Tetrigidae, commonly known as pygmy grasshoppers, are an ancient and diverse family, currently numbering about 2000 species. As their name suggests, tetrigids are very small; their largest representatives are barely several centimeters long, so they might be difficult to spot on a casual stroll through tropical vegetation. However, when they are spotted, they are immediately recognizable by their elongated pronotum, a hard structure that starts behind the head and covers the entire body like a hood. They come in many shapes and colors and are often exciting to see, but this comes with a price—the taxonomy of Tetrigidae, the way they are organized into natural groups, is a mess. This is where we come in.
In our latest paper, we dealt with Choriphyllini, a small Caribbean tribe that belongs to the subfamily Cladonotinae. This subfamily had been filling up with unrelated but similar-looking tetrigids for more than a century. It had never been clearly defined so almost everything wingless and robust was assigned to Cladonotinae. We decided to put an end to this by slowly removing the superficially similar genera from the subfamily and describing tribes to group the genera that are clearly related to each other. We piloted this system just last year, when we described the tribe Valalyllini from Madagascar, with only two endemic (and endangered) genera and species.
Put the species of Choriphyllini and Valalyllini together, mix them up, and try to guess which belongs where—this is no simple task; they are all doing their impressions of dead leaves that our primate brains struggle to differentiate. And there’s more: such leaf-like grasshoppers live in Africa and South East Asia as well, and then there are those that look like twigs and spiky tree bark.
Only now that we have an idea of what the true Cladonotinae are can we be properly amazed by the duality they represent to us. On the one hand, they are incredibly diverse with every species having its own variation on the basic shape. On the other, they are so alike that they either represent the best example of convergent evolution ever documented or they all stem from a common ancestor that is currently supposed to have lived during the Mesozoic. The evolutionary history of Cladonotinae will take many years to unravel, but the work can only begin after we define what to call by that name.
It only took 250 years
The first species of Choriphyllini, Phyllotettix rhombeus, was described in 1765 as Cicada rhombea, that is, as a member of an entirely different order of insects. Continuing in this manner, many authors (including the great Linnaeus himself) made many taxonomic and nomenclatural mistakes that compounded over the centuries and made these grasshoppers difficult to identify and refer to. It didn’t help that new species and new records kept being reported without being contextualized by comprehensive literature reviews. Like detectives, we followed the scattered crumbs of data and arrived at a synthesis that will make future research in the region much more pleasant.
This is not where interesting facts about Phyllotettix rhombeus stop. While looking through the literature, we tried to extract the measurements of drawings. Most of the drawings had a scale bar printed next to them, but the archaic usage of “lines” as the standard measurement initially gave us some trouble. That is why at first we doubted one of our most fascinating discoveries: with the pronotal length measuring nearly 3 centimeters, Phyllotettix rhombeus is the largest tetrigid ever recorded! Many, many authors dealt with this species over the last 250 years, but this record was never made explicit.
It should not go unnoticed now that its proposed common name is “Jamaican Colossal Jumping Leaf”. Inspired by this, we took the measurements of the other species as well and made a figure where all the specimens are resized to a common scale, which shows the diversity of both shapes and sizes.
Besides P. rhombeus, there are three more species in the genus Phyllotettix: P. plagiatus, P. foliatus, and P. compressus. All four of them are known only from Jamaica. P. foliatus and P. compressus are known from the Blue Mountains, but for the other two no precise localities are known; we still don’t know where exactly the largest tetrigid lives. The other genus of the tribe is Choriphyllum, also with four species. Three of them, C. sagrai, C. saussurei, and C. wallaceum live in Cuba, while C. bahamense is all alone on Hummingbird Cay island in the Bahamas. The easiest way to differentiate these two genera is a little strange but practical, the tallest point of the leaf-like crest in Choriphyllum species is in the front, while in Phyllotettix species it is in the back.
Some Caribbean leaves dance and jump
For each species, we proposed a common name as a means to give these animals even more character. Names, such as “Jamaican Bitten Jumping Leaf” and “Old Cuban Dancing Leaf” may not be “official”, but they have certainly found their audience. The tweet in which we shared the collage of all the species was viewed over 17000 times; everyone was amazed by the pretty shapes and some even noted that they especially liked the crazy common names. We were very glad to see our scientific and artistic package that is Choriphyllini be so warmly received.
Another hit on Twitter, with over 20000 views, is the post showcasing the newly-described species from Cuba, Choriphyllum wallaceum. The holotype of this species has been awaiting description for a long time. We found it in Museo Nacional de Ciencias Naturales in Madrid, Spain, with a note from Ignacio Bolívar, the father of the Tetrigidae classification system. He referred to it as “Choriphyllum Seoanei” but never managed to publish it.
This “new” species presented us with the perfect opportunity to honor the 200th anniversary of Alfred Russel Wallace’s birth. Wallace is often called the “father of biogeography” but is all too often neglected when discussing the origins of the theory of evolution, with which Charles Darwin is considered synonymous. Wallace, with his independent arrival at the key concepts of the evolutionary theory, his correspondence with Darwin, and his staunch defense of Darwin’s ideas, was (and is) at the very least equal to Darwin and deserves much more recognition than he currently gets.
This is just the start
Choriphyllini are a pretty package, but one that merely introduces the real problem. The history of this tribe is long, yet we have very few specimens to work with. Although we have an understanding of how morphology varies within species, P. compressus and P. foliatus are not only suspiciously similar to each other, but they also live in the same general area of the Blue Mountains. It remains to be seen if they are in fact a single species.
Much more pressing is that we have only a vague idea of where these animals live and how their populations are impacted by various factors such as human activity and climate change—we do not have a baseline against which to assess their conservation status. Then there is the fact that there are many more islands in the Caribbean, making the possibility of discovering new Choriphyllini species on them real and exciting. We can only guess what the future holds for these neglected animals.
The stage is set; everything we know about this group is laid out in the paper and now there is no path but forward. Research is expensive, dedication to this work takes a certain kind of soul, and everything takes time. It is our sincere hope that someone someday takes this further. The pygmy jumping leaves will wait for as long as they can, on their islands, hopping without a care in the world.
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