Surprisingly high butterfly diversity found in North American deserts

In a new study from Cell Press, experts have found remarkable butterfly diversity in the deserts of Mexico and the southwestern United States. The surprising discovery may be tied to actively changing conditions in the in the western portion of North America.

“When you think of desert, you don’t automatically jump to butterflies, but our results showed that this area is actually a really important hotspot for butterflies, even if it isn’t for plants,” said study co-first author Chandra Earl. “Just because butterflies are closely tied to their host plants doesn’t mean their diversity outcomes have to be similar.”

The researchers conducted a continent-wide analysis using a variety of biodiversity databases, including GenBank, Barcode of Life Data System (BOLD), and Map of Life (@moldotorg). 

The experts did not simply count the number of butterfly and plant species in a given area, but also examined the degree of evolutionary relatedness – or phylodiversity – of species in each region. 

“We wouldn’t have found the same result if we’d just counted the species like most biodiversity studies.” said Earl. “But we really wanted to step away from that, so we didn’t lose the importance of evolutionary history.”

The researchers explained that butterfly diversity may be greater than that of plants in the desert due to how they interact in the ecosystem.

“Most butterflies are generalists that don’t utilize just one host plant. This means that there are a lot of plants with no real functional relevance to butterflies” said study co-first author Michael Belitz. “This makes butterflies less likely to clump into groups of tightly related species like plants do.”

There are other ecological factors that may also play a role in butterfly diversity across North American deserts, including the fact that butterflies are much more mobile than plants. 

“These factors all add noise to the data, where you won’t see as strong a relationship between plants and butterflies as you might expect,” explained Belitz.

The researchers hope that this new understanding of butterfly diversity will encourage others to research and help conserve the insects.

“People already know about the decline of monarch butterflies, but the entire group is under threat,” said Earl. “We need to start paying better attention to insects, and this study helps prioritize North American deserts as a new target for conservation efforts.”

The study is published in the journal iScience.

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By Chrissy Sexton, Earth.com Staff Writer