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"Boring" tropical butterflies have a fascinating family tree

The euptychines are one of the most diverse groups of butterflies in the American Tropics, with over 100 co-occurring species in the rainforests of Peru and Brazil. Since even distantly related species often look very similar, they have not been very attractive to collectors and researchers, and the early naturalists had no method to accurately classify them.

For instance, the German entomologist Jacob Hübner – the first to describe the group in the early 1880s – lumped the few species then known into several genera based on similar appearance.

Now, by using DNA analysis, an international team of scientists has found that there are at least 70 Euptychiina genera, consisting of over 500 species. Moreover, the analysis also revealed that there are at least 130 unnamed species in this group awaiting formal scientific description.

The project of mapping Euptychiina diversity was initiated in 2009 by Keith Willmott, the director of the McGuire Center for Lepidoptera and Biodiversity at the Florida Museum of Natural History, who reached to several researchers attempting to classify these frequently called “brown, boring butterflies” individually, and proposed them to combine their efforts.

A first question was how many groups of Eupychiina there were and how they were related to one another. “The way people would typically work on this kind of problem would be to divide and conquer, but that doesn’t work for euptychiines, because there are very few unifying features among species that you can use to define groups,” Willmott explained.

To overcome this issue, the scientists examined over 60,000 specimens from museums in Europe and North and South America, along with butterflies collected throughout their range, from the foothills of the Andes in Ecuador to the Atlantic Forest in Southeastern Brazil. These investigations helped them document more than 100 new species, many of which were previously concealed by their close resemblance to each other. 

“A recent example is a large butterfly that used to be known as Pseudodebis celia from western Ecuador, which turned out to be four separate species. These are big butterflies. It’s hard to imagine these kinds of species are still escaping detection,” Willmott said.

While many euptychiines are masters of disguise, using mimicry to blend in with their surroundings as well as resemble other butterfly species, others have evolved bright blue scales or blazing orange eyespots, which would assumedly make them easier to classify. However, the results of genetic analyses have shown that such color patterns could be deceptive too, since multiple species have transformed their wings into blue frescoes, making them appear superficially similar.

Moreover, while many innocuous species of butterflies mimic the color of poisonous species in order to deter predators, this does not seem to be the case for euptychiines. “As far as we know, they’re not unpalatable or protected against predators in any way. It looks like mimicry, but there’s really no basis for it. It’s a fascinating mystery that needs study,” Willmott said. Finally, blue euptychiines can play further tricks on experts since this color is sometimes present only in some individuals belonging to a species, such as the males. 

This new, DNA-based classification will help scientists clarify the exact identity of known euptychiines and describe a variety of new species, while setting the stage for scientific forays into other aspects of euptychiine biology.

Image Credit: Photo by Keith Willmott

The study is published in the journal Systematic Entomology.

By Andrei Ionescu, Staff Writer

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