Endangered Hawaiian picture-winged flies play important role in ecosystem restoration

Endangered Hawaiian picture-winged flies play an important role in providing balance to Hawaiʻi’s natural ecosystems, according to researchers.

Scientists and researchers at the University of Hawaiʻi at Mānoa and the DLNR Division of Forestry and Wildlife are working together to re-establish picture-winged fly populations, including of Drosophila hemipeza, an endangered species.

The project’s aim is to help restore ecosystem stability, support natural biodiversity, and reduce the likelihood of the species’ extinction, according to DLNR.

Historically, D. hemipeza populations were found at multiple sites in both the Ko‘olau and Wai‘anae ranges of O‘ahu. Today, their numbers are greatly diminished, and their range is significantly reduced, according to a DLNR news release. It is believed that Palikea, in the Waiʻanae Range, may be the only remaining site for these flies and few are left there, the department reports.

“Contributing factors to their decline include a range of issues that a lot of other native insects face: deforestation, predation and competition from invasives, native host plant destruction from pigs, and climate change,” said Kelli Konicek, Entomological Research Technician with the Hawai‘i Invertebrate Program.

Konicek and a small group of researchers are working to stem that tide, rearing D. hemipeza in a lab to introduce into the wild. Through experimentation and ingenuity working with more common and abundant fly species, and leveraging long-term knowledge developed by UH researchers at the Hawaiian Drosophila Research Stock Center, the team developed an effective mass rearing regimen. 

“I collected four D. hemipeza individuals in May 2022, and by December I had over 1,000 flies emerge,” Konicek explained. “It’s been very successful in terms of rearing, which can be a tricky process. These files are temperamental, temperature-sensitive, and will only lay eggs in certain native plants.”

Rearing is only one aspect of the process. Keeping the flies fit and healthy enough to be introduced into nature is another. Over the last few months, the group has become proficient in that regard. 

Researchers are slowly releasing these flies at a Mānoa Cliff Restoration site, containing several native host plant species in which D. hemipeza are known to breed. Native ‘ōhā wai, hāhā, and ōpuhe have been planted by a dedicated group of volunteers in cooperation with DOFAW’s Plant Extinction Prevention Program. 

Releases began in October 2022 and by early January, Konicek observed the first unmarked D. hemipeza at the site, a sign that the species is successfully reproducing on its own.

“It’s really promising to observe flies at the site that we know are not lab-reared,” said DLNR Entomologist Cynthia King. “However, we’ll need to continue the introductions to increase the likelihood the species will establish in the long-term.” 

“One of the reasons that it’s important to introduce this native species and others is that a lot of work has been done planting native plants and protecting areas,” Konicek explained. “One of the goals for DLNR is to create a holistic, restored ecosystem. These flies have such an important relationship with their native host plants, the big goal is to create interactions to make sure that the pieces of the environment that we are trying to restore are getting put back into place.”

In conservation efforts, small invertebrates and microfauna often receive less exposure and recognition than their larger animal counterparts, but their role in supporting biodiversity and ecosystem health should be noticed, according to DLNR.