Bad at Goodbyes

Rough Transcript

Intro 00:05

Welcome to Bad at Goodbyes.

On today’s show we consider the Florida Semaphore Cactus.

Species Information 02:05

The Florida Semaphore Cactus is a critically endangered flowering cactus native to Southern North America, specifically the Florida Keys, in the United States.

The Semaphore Cactus is a perennial tree-like cactus that can reach heights of up to 7 feet. What we might mistake for leaves, are in fact, stem segments are these flattened, oblong, bright green, pads that grow up to 16 inches long and are held at right angles to the ground. These segments give the cactus its common name as they are reminiscent of railroad semaphore flags. One can almost imagine this cactus waving to us. The pads are covered in areoles, small raised bumps from which the cactus’s spines emerge.

The spines are numerous, hairlike and pink-ish in color; they can grow to over 5 inches long and serve as a means of protection for the plant.

The Semaphore Cactus produces large, showy blooms that have fleshy outer tepals and red inner tepals that can reach 1 inch in length. Tepals are a circular arrangement of floral growth that radiate from the plant instead of like petals. Flowering occurs year-round, with a peak season from December through April. The flowers emit a scent reminiscent of rotting meat, which attracts pollinators, and once fertilized produces a small yellow berrylike, egg-shaped fruit.

The Florida Semaphore Cactus reproduces both sexually and asexually. It is dioecious meaning the male and female reproductive organs are on separate individuals. Though its flowers have vestiges of both organs, some cacti are functionally male, some are functionally female. It cannot self-pollinate.

Sexual reproduction occurs when the flowers attract pollinators, specifically ants, who feed on and spread reproductive material, pollen, from the stamen on male plants to the stigma on female plants. Upon successful pollination, the flowers develop into fruits containing seeds, these yellow berries.

Seeds have been observed to begin to germinate, to sprout, while still inside the fruit, after it falls off the plant. This helps the seedlings avoid drying out during dry periods. The seeds themselves are encased in a structure called a funiculus, which also seems to slow down germination. This delay is beneficial as it takes about 4 months for the seeds to sprout, allowing them to avoid germinating during dry months.

However, seed production in the Semaphore cactus is relatively rare and the viability of the seeds is often low. While seeds that were collected in the wild and planted in captivity were able to grow, there have been no observed new seedlings in their natural habitat.

And so their more common reproduction method is asexual, also called vegetative propagation. Stem segments, the pads, can detach from the parent plant and root in the ground, establishing new individuals. This clonal reproduction leads to genetically identical plants, and the cactus will form small colonies of parent and pup. “pup” is adorably the term for these asexually reproduced offspring, though also called offsets, by less delightful botanists.

The Florida Semaphore Cactus is native to a very specific and limited habitat in the Florida Keys, on Little Torch Key and Swan Key.

This habitat is characterized by a tropical maritime climate with high humidity, abundant sunshine, and average annual temperatures ranging between 70 and 85°F. The region experiences a distinct wet and dry season, with the majority of rainfall occurring from June to October, seeing approximately 40 inches of rain annually.

These island landscapes are primarily rocky limestone substrate beneath a thin layer of humus. Humus is this dark organic soil matter formed by the decomposition of plants and animals. It is rich in nutrients and retains moisture.

The Semaphore Cactus grows in these rock barrens, on exposed rock surfaces, in crevices, or within small pockets of soil. 

This landscape is an ecotone between stands of freshwater hardwood trees and saltwater mangrove swamps. Ecotone just means the transition area between two biomes, where two ecological communities meet and integrate. It is quite near sea-level, it’s relatively flat, with slight elevation changes near the coastline.

The Semaphore Cactus’ ecotone is rich with biodiversity, supporting mangrove, crocodile, salt couch grass, buttonwood, green iguana, beach apple, land snails, great white heron, spoonbill, spiders, sea grape and butterflies.

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In the dream it is the soft light of morning, and in the dream the waves perform their forever circular geometry, they seem to have a question for me, they draw nearer and nearer, whisper louder and louder. It is the same question the moth asks, and the human and the hurricane. “For whom do you wait?” they wonder. I don’t know. In the dream, I don’t know.

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The range and population of the Florida Semaphore cactus has been substantially reduced by human development. It once thrived throughout the Florida keys and scientists believe it may have even held purchase on the mainland. Now, due to decades of human intrusion through housing, road and recreational development, it survives only in two small isolated populations on Swan Key and Little Torch Key. The population on Little Torch was significantly threatened by poachers until it was protected by the Nature Conservancy in 1988.

Now, the most immediate threat to the remaining populations are a non-native, human-introduced invasive moth species that eats the cacti.

Human generated pollution and the effects of human-induced climate change also challenge the cacti. Increased hurricane activity and sea-level rise due to global warming risk overtaking the cacti with saltwater. Conservationists also report continued poaching and vandalism.

The species’ low population and reproductive strategy presents a longterm hurdle.

Through the second half of the 20th century, the Semaphore Cactus population on Little Torch Key was reduced by poachers stealing and selling the plants for rare ornamental gardens. Resulting in a small population of genetically similar individuals.

Quick sidebar on the genetics of sexual reproduction, I’m simplifying here, but in general, for like most plants and animals, offspring are roughly half female and half male but the process is in fact random, it’s a mostly random recombination of chromosomes.

And so with the Semaphore Cactus the random assigning of gender over recent generations (coupled with the additional stressors mentioned before) has resulted in the current population on Little Torch Key believed to be all male. And so, all of its offspring are produced asexually and are genetically identical. And remember they cannot self-pollinate. It is the end of their evolutionary journey.

This is an immediate issue because some of this population is suffering from root rot due to fungal infestation. The current population is not adapted to combat this infestation, and all future generations are vulnerable because they are genetically identical. Natural selection is thwarted and the species is incapable of developing a random genetic mutation that might result in an adaptation that can protect or fight off the infestation in future generations.

And we might think that “well this is evolution, some species succeed, others do not.” But in this case, it is not like true natural selection, it’s not real evolutionary competition because humans have put their opposable thumb on the scale.

So the short version: Human induced genetic bottleneck leads to an inability to sexually reproduce viable offspring which results in an inability to adapt to new stressors. Which will likely lead to extinction.

The Florida Semaphore Cactus does have international legal protection and all of the known populations are within protected wildlife areas.

The Florida Semaphore Cactus was placed on the Critically Endangered Red List in 2013, their population is currently in decline.

Our most recent counts estimate that less than 500 Florida Semaphore Cactus remain in the wild.

Citations 18:40

IUCN – https://www.iucnredlist.org/species/16329591/16329597

PBS – https://news.wgcu.org/2020-01-13/as-seas-rise-a-florida-keys-ghost-forest-makes-a-last-stand 

US Fish and Wildlife Service – https://www.fws.gov/species/florida-semaphore-cactus-consolea-corallicola

The Journal of Sexual Plant Reproduction; Volume 11 – http://dx.doi.org/10.1007/s004970050143 

Wikipedia – https://en.wikipedia.org/wiki/Consolea_corallicola 

Music 19:58

Pledge 29:01

I honor the lifeforce of the Florida Semaphore Cactus. I will carry its human name in my record. I am grateful to have shared time on our bright planet with this being. I lament the ways in which I and my species have harmed and diminished this species.

And so, in the name of the Florida Semaphore Cactus I pledge to reduce my consumption. And my carbon footprint. And curb my wastefulness. I pledge to acknowledge and attempt to address the costs of my actions and inactions. And I pledge to resist the harm of any kin or their habitat, by corporations and governments.

I pledge my song to the witness and memory of all life, to a broad celebration of biodiversity, and to the total liberation of all beings.