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Rainfall patterns will decide if Miami blue butterflies can survive

Often when the ideas of species survival and climate change come to mind, the image of a polar bear on a melting iceberg is conjured. A new study looks not at warmer weather, but at changing rainfall patterns associated with climate change, to predict the fate of the Miami blue butterfly (Cyclargus thomasi bethunebakeri).

The Miami blue butterfly is a federally endangered species that can be found exclusively in a small habitat in southern Florida. Like many tropical or subtropical insect species, the Miami blue butterfly goes through a period of diapause in which larvae pause in their development during a dry season.

The beginning of the rainy season causes the end of diapause. Longer dry seasons mean that less butterflies will reach maturity and reproduce compared to the outcome of a short dry season.  

“We found that shifting rainfall patterns can determine whether the Miami blue butterfly populations grow or shrink, even without any other environmental variables changing,” said study lead author Erica Henry, a postdoc in Applied Ecology at NC State.

“This is not only concerning for this rare butterfly, but for all insects in precipitation-driven systems. Both the tropics and rainfall patterns have been largely overlooked in the conversation about climate change and animal lifecycles.”

Many insects have life stages triggered by precipitation, and it is uncertain how a changing climate will impact each of them. Some parts of the planet are predicted to become drier, while other regions will become wetter. 

In places like southern Florida, it’s been difficult to predict how rainfall will change. Due to this uncertainty, the scientists have modeled 20 different climate scenarios to see how each would impact the Miami blue butterfly. In most scenarios with longer diapause periods, these butterfly populations dropped. 

“The tropics, and more specifically that fuzzy area we call the sub-tropics, covers an extremely diverse set of ecosystems that are much more sensitive to projected shifts in precipitation than temperature,” said study co-author Adam Terando, a U.S. Geological Survey Research Ecologist and adjunct professor in the Department of Applied Ecology at NC State. 

“The problem is, there’s also a lot more uncertainty about those precipitation changes as the planet warms. We wanted to bring attention to these rainy-season ecosystems and demonstrate how linking climate science with ecology can give us new insights into what to expect in the future.”

This research is important in being one of the first studies to focus on how changing rainfall patterns impact tropical insects. It’s a critical step in protecting these and other beautiful creatures. 

The study is published in the journal Climate Change Ecology.

By Zach Fitzner, Staff Writer

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