Jackie Minett is a tour guide at Butterfly World in Coconut Creek, Florida, dubbed the “butterfly capital of the world.” She leads children and seniors, some tourists, some Floridians, around the gardens to gawk at butterflies: zebra longwings, emperor butterflies, and the most recognizable of all monarchs.
South Florida’s monarch population is one of the few known non-migratory populations in North America. Minett jokes that’s because “they have it so good” and “it’s like people retiring in Florida.”
But when the International Union for Conservation of Nature listed the migrating monarch butterfly as endangered in late July, South Floridians like Minett began to wonder what that meant for the region’s more settled subspecies.
A safety net in South Florida
Minett contends that Butterfly World has been especially busy the past few weeks. Customers flock in with questions about the monarchs: “We heard it made the endangered list,” “Where can I buy milkweed,” and “What can I do to help?”
Part of the misconception behind the International Union for Conservation of Nature’s endangerment listing is that it applies to all monarch butterflies. The listing applies to only migratory monarchs, a subspecies of the butterfly that doesn’t include South Florida’s native non-migratory population.
“The Florida population is kind of an unusual beast in that there’s three different things happening down in South Florida,” said Jaret Daniels, an insect conservation biologist who is curator at the Florida Museum of Natural History’s McGuire Center for Lepidopteran Biodiversity.
Apart from the non-migratory subspecies, there are migratory monarchs that treat Florida as an annual rest stop on their way back from Mexico and those that use Florida as a winter breeding location.
“So it’s kind of a muddied mess of different types of behaviors and population dynamics,” Daniels said.
Part of the reason why migratory monarchs were listed as endangered is habitat loss. Florida, ever-straying from the norm, has a unique version of that problem: too much habitat.
Milkweed is the host plant monarchs need in order to reproduce. The butterflies lay their eggs on the milkweed, and when caterpillars hatch, they feast on the plant’s leaves. There are more than 20 species of milkweed native to Florida, less than half of which are native to South Florida.
But the most common milkweed plant found around the state is not native at all. That’s the issue.
Tropical milkweed, or asclepias curassavica, is an invasive milkweed plant that’s spread wildly across Florida. It manages South Florida’s consistent heat well, but is also resilient enough to withstand the winter temperature drops in the northern part of the state. It grows year-round and can be found across the Deep South, but Florida is more covered in it than anywhere else in the country.
Its durability and golden orange blooms make it a popular purchase among gardeners. So popular that it’s become more difficult to source native milkweed plants.
“Growers feel like there’s not as much market for native milkweed, but the public wants native milkweed, so there’s a little disconnect,” Daniels said. “There’s incredible need and desire from the public. It’s just the nursery industry hasn’t quite caught up to this overall.”
Consumers are after native milkweed species even with an abundance of tropical milkweed, which lasts far longer and has more picturesque blooms than the majority of its native counterparts. The reason: Tropical milkweed is also a popular host for a parasite that’s killed tens of millions of monarchs.
A parasitic problem
Minett likens the monarch’s chrysalis to a jewel. In her eyes, it resembles a piece of jade with “drops of gold and a crown of pearls,” fitting for an insect named after royalty.
But when a pupae is infected with ophryocystis elektroscirrha, or OE, she said that jewel tone turns a sickly black. Sometimes those chrysalides don’t hatch. When they do, they turn into far weaker, disease-ridden monarchs.
Florida is ground zero for OE. Not only is it the first place where the parasite was discovered, it’s also the most infected state in the country. Monarch Health, a community science project based out of the University of Georgia, estimates that South Florida’s monarch population is entirely infected.
The parasite waits for monarchs on milkweed plants as spores. When a female monarch goes to lay its eggs on a milkweed plant that carries OE, thousands to millions of spores can attach to its body. That butterfly will then infect its offspring by scattering the parasite onto its eggs. Once a caterpillar hatches, it eats the spores on the infected egg shell and leaves, while the mother monarch carries her spores onto the next plant and spreads the disease.
Since tropical milkweed grows so well in Florida, infected plants last longer and have ample opportunity to pass the parasites to as many monarchs as possible.
“We know from lab studies that parasitized monarchs don’t fly very well; we know their wings are more brittle; we know they have less energy,” said Andy Davis, a research scientist at the University of Georgia’s Odum School of Ecology who has studied monarchs for more than 20 years. “A whole bunch of things are sort of working against them if they have this parasite.”
This means migratory monarchs, many of which claim Florida as an important stopover point, may not be strong enough to make their migration if infected. What’s endangered may not necessarily be the fate of the monarch butterfly itself, but rather the fate of its migration.
“People would say to the late Lincoln Brower, a world famous monarch scientist for many years, ‘What’s the good of this migration? What good is it for the world?’ And his answer would be ‘Well, what’s the good of the Mona Lisa?’ The migration is kind of the same thing,” Davis said. “It’s this natural wonder that instills excitement.”
Monarch butterfly populations are thriving in North America
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Citation: South Florida’s monarch population is an ‘unusual beast.’ Some butterflies are endangered, but these plan to hang around (2022, August 11) retrieved 11 August 2022 from https://phys.org/news/2022-08-south-florida-monarch-population-unusual.html
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