image: Kasey Fowler-Finn, Ph.D., assistant professor of biology at Saint Louis University. view more
Credit: Ellen Hutti, Saint Louis University
ST. LOUIS - Thanks to a recent $480,000 grant from the National Science Foundation (NSF), Kasey Fowler-Finn, Ph.D., assistant professor of biology at Saint Louis University, and her laboratory are poised to learn more about how changing temperatures, like those caused by global warming, affect singing insects' behavior, particularly their ability to recognize the songs of potential mates.
Insects play key roles in our ecosystems, affecting the pollination of food crops, nutrient cycling and the movement of diseases.
"Some insects are pests to crops and some help break down and recycle nutrients and play important roles in the food web," said Fowler-Finn. "If some species drop out because changes in temperature makes it hard to reproduce, an entire ecosystem could struggle because it's lost a key player."
Using controlled laboratory conditions, Fowler-Finn's team is conducting experiments that look at how temperature variation affects reproduction, and the potential role of genetics in singing insect evolutionary responses to temperature changes.
In addition to learning more about global warming's potential impact to insects and ecosystems, the study team also is partnering with artists and community organizations to help educate the public about the vital role and fascinating attributes of vibrationally singing insects through a sound installation exhibit at Saint Louis University Museum of Art (SLUMA) and exhibits at the St. Louis Zoo.
Fowler-Finn studies half-centimeter-long insects called treehoppers that are found across a wide swath of North America, from the southern U.S. to southern Canada. These tiny insects spend their entire lifecycle on a single species of plant, the wafer ash (also called hop tree), subsisting on the trees' sap.
Treehoppers create their songs not by creating an airborne sound picked up by ears, but rather by producing vibrations that travel through the plant stems where they are picked up by a listening treehopper with sensitive organs in their legs. These songs are referred to as substrate borne vibrations, and while imperceptible to humans, this is a surprisingly common communication tactic in the animal kingdom.
Many insects and arachnids use substrate borne vibrations, and even larger mammals like elephants communicate this way--with calls that travel through the ground to be picked up by other elephants through their feet and trunks--as well as and kangaroo rats and mole rats, which can communicate with thumps and navigate by listening to how sound bounces off of objects underground.
In order to listen in on the secret world of vibrations, the Fowler-Finn lab uses a variety of recording devices, including accelerometers, piezo discs, guitar clips, and lasers, a student favorite.
During the mating season, male treehoppers fly from branch to branch producing advertisement signals. Females listen to these songs to identify good mates of the correct species in order to successfully reproduce. If they are interested, females sing back, and a male-female duet ensues until mating occurs.
Fowler-Finn and her team want to know how temperature variation may disrupt this delicate coordination of mating. Researchers know that airborne insect songs and behavior used to attract mates vary with temperature, and Fowler-Finn's team has shown the same to be true for vibrational signalers like treehoppers.
"There is a thermal window when treehoppers are most active," Fowler-Finn said. "Outside of that window, they just don't do much. With global warming we see more temperature variability, temperature shifts and less predictability, and therefore less time in that optimal thermal window. So, any sort of temperature shift can throw them off.
"For example, males at different temperatures sound like different species, and this can be confusing to the females."
The SLU team hopes to find insight into how genetic variation may give some treehoppers a survival advantage even under the threat of temperature change.
"Evolution happens at the population level, and it's possible that some populations might be better able to adjust to temperature changes. We will see if any of the populations we are studying have a genetic advantage to evolving to continue to be able to mate under circumstances where the temperature varies."
The project also includes two components that are intended to educate and engage the general public.
The research team will begin a collaboration with a sound artist to create an experience that brings the otherwise imperceptible sounds of singing insects' songs to a human audience through a sound installation. The exhibit is slated for year two of the project and will be on display at SLUMA.
A second collaboration will bring immersive sound installations, insectarium exhibits, and online videos and resources that educate the public about vibrational songs to the St. Louis Zoo.
"We're helping the Zoo construct part of their insectarium," Fowler-Finn said. "Students on my lab team are designing information placards and thinking about local, regional and countrywide insects, and the different ways they communicate, via chemicals, airborne sounds and substrates. We'll work with the Zoo to design this."
The lab team involves undergraduates, graduate students and post-doctoral researchers who gather for weekly lab meetings to plan the work that will go into the many elements of this three-year study and accompanying outreach projects.
"That's the fun thing about having these big projects," Fowler-Finn said. "Depending on their interests, students can participate in any of several projects aimed at increasing the world's knowledge about singing insects."
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