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New Insights into the Coevolution of Hawaiian Crickets and Parasitic Flies

Male crickets in Hawaii are facing an evolving challenge from parasitic flies that have adapted to their mating signals.

Recent research published on February 20 in Current Biology reveals that parasitic flies, specifically Ormia ochracea, have developed heightened auditory sensitivity to the altered mating calls of Pacific field crickets (Teleogryllus oceanicus), which have undergone significant changes since the introduction of the flies to the islands around 1989.

These nocturnal flies deposit their eggs on crickets, and when the larvae hatch, they consume the host from the inside. Following the flies’ arrival, some male crickets in Hawaii evolved distinctive wing shapes that produce unique purring or rattling calls. This adaptation likely helped them communicate with potential mates while minimizing their detection by the flies. However, researchers speculated on whether the flies would also adapt to this new form of communication.

“Will the fly respond to these changes, or will crickets be able to establish a communication method that the flies cannot intercept?” poses Robin Tinghitella, an evolutionary and behavioral ecologist from the University of Denver.

In a controlled experiment, Tinghitella and her team examined the auditory responses of O. ochracea flies from both Hawaii and Florida. They assessed how the flies reacted to different sound frequencies and the various cricket songs. Their results showed that the Hawaiian flies demonstrated increased sensitivity to sounds in the 5 to 10 kilohertz range, which coincides with the frequencies of typical cricket and purring calls.

Moreover, when the team tested the Hawaiian flies with recordings of these cricket songs, they found that around 20 percent were attracted to the purring calls, suggesting that the new cricket calls—freshly evolved within a decade—are already on the radar of the flies.

According to Tinghitella, these observations reflect a dynamic process of adaptation and coadaptation, hinting at a potential evolutionary arms race between the crickets and the flies. As O. ochracea becomes adept at detecting the modified cricket calls, it raises questions about how the crickets will respond in turn.

Norman Lee, a neuroethologist and co-author of the study from St. Olaf College, emphasizes the importance of collecting more data on the auditory capabilities of the flies to help predict the forthcoming evolutionary strategies of the crickets. This lively interplay could shape the evolutionary landscape for both species in the years to come.

Source
www.sciencenews.org