Answer: How can the same locust look so different?

 

It's difficult to understand... 

Rocky Mountain locust. P/C Wikimedia

... how variable the appearance of an animal might be.  In this case, how can this particular insect--the Rocky Mountain locust--be so variable in appearence that biologists thought that the two different forms of the insect were actually different species?  

So how could biologists mistake the two different looks of a locust for two different species?  

1. How often has it happened that biologists have seen two (or more) species when it was really just one in different clothing?  Can you find another case of two (or more) species being reconciled into one? 

This seems like a great question for an LLM.  When I copy/pasted this into Gemini, I learned that this happens more often than I thought.  The Gemini answer talked about "lumping" and "splitting" a species definition--by "lumping together" two organisms that were thought to be different, and "splitting apart" organisms that look the same, but are actually genetically different.  

That sounds right, but the words "lumping" and "splitting" are probably NOT what biologists call this process.  

A quick query of: [what do you call it when biologists find that two different appearing animals are found to be the same species and they reclassify them in a new species name] taught me that biologists refer to this process (which happens a LOT), as synonymization. ("Synonymization" is the process of identifying and combining different scientific names that refer to the same organism. This happens when a species is described multiple times by different scientists, or when a species is reclassified into a different genus, or when different organisms are discovered to be variants of a common organism.)

I revised the question to learn about "splitting" and learned that this is just regular old speciation, which then leads biologists to a taxonomic revision in the textbooks.  

This is often the result of cryptic species, which are species that appear identical but are reproductively isolated.  

To find examples of "splitting" I asked the obvious query: [can you give me examples of organisms that seem very similar and were once thought to be one species, but are now understood to be multiple species?]  and found several examples.  The elephant in the room is obviously the African elephants...  

African elephant (Loxodonta africana).  P/C K. Russell

Historically classified as a single species, the African elephant, has now been distinguished as two separate species: the African bush elephant (Loxodonta africana) and the African forest elephant (Loxodonta cyclotis). They have nearly identical appearances, but DNA analysis revealed them to be genetically distinct and reproductively isolated, with the forest elephant being slightly smaller and having straighter tusks.

And the converse:  [can you give me examples of organisms that seem very different and were once thought to be different species, but are now understood to be just one species?] 

Leptocephalus, the larval form of Anguilla anguilla. Yes, they are transparent.

A lovely answer:  For centuries, the transparent, ribbon-like leptocephalus larva was believed to be a separate species from the adult eel (Anguilla anguilla). It was only in the early 20th century that scientists realized the leptocephalus is the eel’s larval stage and not a different organism.  

And when I asked about locusts in particular, I learned that for centuries, naturalists thought that the grasshopper and the swarming locusts were entirely different insects. (For the record, they also wrote that caterpillars and butterflies were completely different insects as well...)  

The solitary form of the locust lives alone as a grasshopper, while the gregarious or swarming form appears during outbreaks.  It's larger, brightly colored (often yellow and black), with longer wings, stronger flight muscles, and completely different behavior, preferring to fly in massive swarms.  

They were so different in appearance and habits that early entomologists gave them different scientific names. 

Then, around one hundred years ago (1921), Sir Boris Uvarov recognized that two locust species are one species but appearing in two different phases, a solitarious and a gregarious phase.  This phenomenon of phase polymorphism, is now called polyphenism.   (See a nice review paper on Uvarov's discovery, "One hundred years of phase polymorphism research in locusts.") 

It turns out that under crowded conditions, young locusts experience tactile stimulation on their hind legs and undergo phase transformation, triggering massive physiological and behavioral changes. This transformation affects color, size, brain structure, metabolism, and social behavior, switching them from a solitary to a gregarious form — leading to the famous locust swarming behavior.  

2. It's clear that organisms can have multiple shapes / patterns / colors (we've discussed this before in the context of plant mimicry).  Can you find an organism that has a huge number of different appearances?  Any idea WHY they have such variability?  

 

I put this question to Claude as [Can you find an organism that has a large number of variable appearances?  That is, what is the most polymorphic organism?]

All of the AIs--Claude (and Gemini and ChatGPT)--gave variations on a good answer, pointing out that both the Great Mormon Butterfly (Papilio memnon) and certain snails (e.g., the Grove snail, Cepaea nemoralis) are famous for their polymorphism, leading biologists to classify the different forms as different species.  

Polymorphisms in Papilio memnon.  P/C Wikimedia

The Grove snails have widely varying shells, which can be different colors (brown, pink, yellow) and have various banding patterns. These different morphs can look so distinct they puzzled early researchers, and the variety is controlled by a complex of closely linked genes.

Polymorphism in Grove snails (Cepaea nemoralis). P/C Wikimedia

And there's the answer: there are many organisms with widely varying morphs--ants, bees, fish, snails, and locusts.  

WHY this is so can be seen in the many shapes of dogs around the world.  How can one species be SO variable in size, shape, and color, yet all be one species?  

Another LLM query:  [what are the genetic factors the cause extreme polymorphism in some species?]   You can do that query yourself and read the details, but it boils down to this: there are a small number of genes that control a LOT of the variation in coat kind, coat color, size, muzzle shape, etc.  With a great deal of selective breeding over the eons (by people), the variation has been amplified into the great number of dog varieties that we see today.  (For lots of insights, see:  Boyko, Adam R., et al. "A simple genetic architecture underlies morphological variation in dogs." PLoS biology 8.8 (2010).  

Search Research Summary

1. The AIs worked well.  One of the nice surprises of this Challenge is how well the LLMs answered each question.  This is largely due to this being a not-especially controversial area--nobody bothers to push out pathological content about the genetics of insects or dogs.  

2. Double check everything.  HOWEVER... for each result I write about here, I double-checked each claim.  In some cases I triple checked. It's just what you have to do these days. 

On the upside, most of the explanations were quite good.  (The business about "lumping" and "splitting" aside--those are common terms that work well, but are not terms of art.)  

A few times I had to dive a little deeper into the topic area to fully understand what was going on.  But that's a big part of The Joy of Search.  

Hope you enjoyed this week's Challenge.  

Keep searching.