Saving Florida's only population of rare, endangered orchid from extinction

Researchers have pinpointed the biggest threats to the only population of rare, endangered mule ear orchids in the U.S.

The Florida International University (FIU) orchid research team found powerful hurricanes can wipe out these fragile plants, but an invasive species of scale insect that feeds on the leaves is the primary culprit of concern.

The findings were published in Ecosphere.

"Mule ear orchids we observed that had scale insects were more likely to die," said Haydee Borrero, the study's lead author and FIU postdoctoral scientist. "This is an invasive species that has impacted other types of orchids on Florida's west coast. So, it's something we need to be worried about."

Borrero, along with FIU conservation ecologist Hong Liu, have long been sentinels for mule ear orchids. These orchids exclusively grow throughout the Caribbean, with the largest populations scattered across remote regions of Cuba. Their northernmost range is south Florida's buttonwood hammocks in Everglades National Park.

As a part of her Ph.D. work at FIU, Borrero traveled to Cuba to conduct fieldwork to better understand these understudied orchids, and found that the ones in Cuba lacked the invasive scale insect that is known to cover the leaves of mule orchids in Florida.

Those leaves—as the name suggests—resemble the big floppy ears of a mule. When this species of scale insect attacks the leaves, it cripples the plant, causing it to shrink in size. When the team returned to a study site where the scale insects had been observed on orchids two years prior, many of the affected plants were dead.

The loss of even a single adult mule ear orchid can be devastating, Borrero said. That's one less plant in an already small population to make the next generation of much-needed orchids, moving them closer to extinction.

"This has been a very important and exciting project, because we were able to do an analysis using many years of data to better tease apart which impacts cause more damage," Liu said. "What we found is complex. It's not straightforward. Yes, hurricanes are a threat. But herbivory is a bigger threat."

In 2017, Hurricane Irma caused its share of damage when storm surge from the category 3 storm stretched across the southern Everglades. While the hurricane damaged the orchid population, it also did a lot of damage to the scale insect population. With fewer insects in the years following Irma, the mule ear orchids went into recovery mode.

Borrero and Liu keep watch and are using this data to help devise future management strategies, and possible rescue strategies for the endangered orchid.

The healthier Cuba populations are a sort of blueprint because they also grow in coastal regions prone to hurricanes and flooding. However, the forests they live in have a greater diversity of tree species. This important information can provide clues on which areas in Florida, with similar types of trees, might be a good fit to relocate and expand Florida's imperiled population.

"One of the reasons we did this research was so we could make more informed [conservation] recommendations—like, what do the habitats look like in Cuba? And do we have similar habitats in Florida that we could plant and introduce these plants," Borrero said. "One idea is to look at the Royal Palm Hammock area [within the Everglades National Park], it has [habitat] characteristics that match populations [in] Cuba."

In the meantime, FIU's orchid team refuses to give up on Florida's mule ear orchids. For Borrero, the mission couldn't be simpler.

"They will go extinct if we don't do anything. If we help them, they will survive."