Acrostichum danaeifolium (acros= tip, stichum = row, referring to rows of spore cases I guess.  Danae was a mythological Greek princess and mother of Perseus.   A plant genus, Danae, honors her, so I’ll take a guess that “danaeifolium” reflects similarity of the fern leaves to those of Danae.)

Pteridaceae, Maidenhair Fern Family

Distributed from Jacksonville to Brazil,  Giant Leather Fern is one of only two (or three) Leather Ferns in the world.    (The similar Acrostichum aureum has one known occurrence in PB County.)   Not only is Acrostichum widespread in space, but also in time, dating back at least into the Cretaceous Period.  This fossil from Spain (discovery and photo by Rafael Moreno-Dominguez) doesn’t look much different from this current specimen (discovery and photo by John Bradford).

An oddity of Leather Fern was noted by plant ecologist Dan Janzen some time ago who raised the question, “why don’t mangrove forests have a more diverse understory than just Leather Ferns?”   (He had no answer.)   

By JB

A simple-minded partial answer that would not have impressed Dr. Janzen, as I see it,  is what habitat on Earth could be worse than the mud under mangroves?  Salty! Deeply shaded! Oxygen-starved! Tides!  Moving sand and mud!   Crabs grazing!   Microbes and algae!   It is a truism in Ecology that horrid habitats make for low species counts.    But the survivors have a monopoly.    And Leather Ferns do a good job of owning the habitat.   In the photo below you can see some competitors trying to establish below Leather Fern along brackish Jones Creek in Jupiter.  No doubt those upstarts are doomed, if salty tidal water doesn’t pickle and smother them, fern-shade will.

It must be rough for seeds to establish in mangrove mud, but Leather Fern has a huge advantage by not having seeds.  Its millions of dustlike spores  “blow all over the place,” including dead branches, hummocks, and raised spots  where conditions are less harsh,  facilitating establishment.      Oddly, the tiny reproductive individuals that hatch from the spores can go through their sexual cycle in  a matter of weeks rapidly before “trouble can strike,” and they change from starting out unisexual, to becoming bisexual and apparently able to fertilize themselves as plan-B.  To be even more certain of standing its ground, the fern buds clonal babies off its rhizomes running through the mud.

Meanwhile back in the Cretaceous