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Florida's flamboyant mule ear orchid, one of its rarest, is in danger of disappearing

The Cape Sable orchid, also known as the mule ear orchid, can now only be found in one location in South Florida, growing on coastal buttonwood trees.
Haydee Borrero
/
Florida International University
The Cape Sable orchid, also known as the mule ear orchid, can now only be found in one location in South Florida, growing on coastal buttonwood trees.

Along South Florida’s remote and rugged Everglades coast, the rare and flamboyant Cape Sable orchid has managed to survive poaching, repeated lashings by hurricanes and even a parasitic fly that feasts only on the stalks of this particular native orchid.

Now, in a study published in the journal Ecosphere last month, scientists worry the cascade of woes may have reached a tipping point with the addition of a new invasive pest.

“It’s comparable to a Category 3 hurricane,” Haydee Borrero, a researcher at Florida International University’s Institute of Environment, said of the tiny scale insect her team discovered attacking the orchid in the southern Everglades.

Across its Caribbean range of growth, the floppy-eared orchid stands out among its peers with dramatic yellow and wine-colored frilly flowers growing on stems that can reach six feet. The trophy orchid, more commonly known as a mule ear orchid, has long been coveted by the plant trade and came under international trade law protections in the 1970s. Its most precarious home has become the southern Everglades, its location closely guarded by researchers and the only place the orchid can be found in North America.

In 2020, federal wildlife managers rejected a request to have the orchid added to the endangered species list. At the time, too little was known about the orchid, said Hong Liu, an FIU ecologist and professor who co-authored the study.

“There was some information, but not enough. How are those populations doing in Cuba and even in the U.S., whether it’s declining or is it stable. We didn’t have much data,” she said. “Now we do.”

The leaves of the orchid range from green to rust-colored.
Haydee Borrero
/
Florida International University
The leaves of the orchid range from green to rust-colored.

For the study, the research team traveled to Cuba and worked with the National Herbarium to look at the largest remaining collection of mule ear orchids spread across eight different locations on the island. In South Florida, the northern boundary of its range, its population had shrunk to one location, where the team located just under 300 orchids.

At the turn of the century, the largest assortment of orchids in the U.S. bejeweled Florida forests, growing across the Big Cypress swamp and the Everglades. Orchids had been traded for thousands of years, but the Victorian era was next level and in Florida, poachers scoured the swamps.

“Extraction from wild populations took place by the wagon load,” Borrero said. “There are these black and white images in historical archives in South Florida that show orchids taken from trees.”

Huge swaths of the Big Cypress were also logged, shrinking the habitat for the tree-loving plant.

While the Cuban population had been poached, which Borrero said remains a threat, the orchid fared better. So what differed? The arrival of the invasive scale.

Borrero and Liu said they were first drawn to the mystery by the freckle-sized fly, not the scale. The fly lays its eggs on the stem of the mule ear flower. The larvae then chow down, damaging the plant but not killing it.

“As a conservation ecologist,I really wanted to get to the bottom of it and see how extensive this problem is,” Liu said. “What is the impact of that particular herbivore on the entire population in South Florida and whether we're actually facing a local extinction probability.”

First identified in the 1970s, the fly only lays its eggs on the mule ear orchid. The researchers found the fly present everywhere they examined the mule ear orchids. But in South Florida, they found the concentration of flies higher than in Cuba and the number of orchids thinned out.

That’s also when they discovered the invasive scale pest, which has attacked orchids globally, had made its way deep into the Everglades.

Haydee Borrero documenting orchids in Southwest Florida last year.
Charles Eglie
/
Florida International University
Haydee Borrero documenting orchids in Southwest Florida last year.

“We didn't know the scale insect problem going into this study. We were just focusing on the flies and that very particular specialist type of interaction,” Liu said.

In 2005, the insect, more commonly known as an armored scale called boisduval scale, was identified as the most damaging scale pest for orchids in Florida and among the top 50 worldwide. The pest was likely introduced to the U.S. by the horticulture trade over the last several decades, escaping from greenhouses and into the wild, Borrero said.

The insects leave behind a powdery white fluff and infestations are almost always lethal.

When the team modeled out the magnitude of the potential damage, Borrero said it amounted to being hammered by a major hurricane. Thankfully, they found no evidence of the scale in the Cuba populations.

But in South Florida, the orchids may need some help if they are to survive.

Among the solutions are some already tested solutions. Seeds can be collected and stored to preserve genetics. Those seeds can also provide nursery-grown orchids for replanting.

“Orchid seeds are quite small. They're dust-like and dry, and they actually freeze quite well,” Borrero said. “So plants can be reared in greenhouses When they get to a certain size, deemed more robust and healthy, they can actually be outplanted into wild populations to augment and boost and bring more genetics into current populations that might be declining.”

In the Big Cypress National Preserve, nursery-bred cypress trees are used to replace trees damaged by oil drilling operations.

On the left, an active infestation of the invasive scale on an mule ear orchid. The right shows yellowing leaves on a dying orchid.
Florida International University
On the left, an active infestation of the invasive scale on an mule ear orchid. The right shows yellowing leaves on a dying orchid.

The U.S. Fish and Wildlife Service could also reconsider adding the orchids to the endangered species list using the additional information. Liu said the team has talked to federal scientists about reconsidering the listing.

Aside from their beauty, Borrero and Liu said the orchids also make for another charismatic indicator of the health of South Florida’s remote coast, particularly as climate change drives up sea levels and erodes coastal forests.

“Honestly, orchids make very good model systems to compare to even animals,” Borrero said. “The plant itself is stationary, which makes it great to survey. You will either find the same plant that you've seen before, or something happened to it. But it also disperses its next generation, almost like a bird does.”

Jenny Staletovich is WLRN's Environment Editor. She has been a journalist working in Florida for nearly 20 years. Contact Jenny at jstaletovich@wlrnnews.org
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