Speculative Biology Sunday: Seacad

5 Dec

Hooray for a new SBS! Don’t you all just love reading the massive slabs of text I write out under these things. I got the idea for this one when I was at the coast, there were cycads everywhere and I enjoyed that fact very much. And of course I began to wonder what cool things cycads could or could have done throughout their evolutionary history. I’m not sure whether the seacad is alternative evolution or future evolution, because it could actually be both; either a future evolutionary development or an extinct form from the height of their diversity which we haven’t found fossils for. Anyway, on with the show.

The Seacad
Seacads are a monophyletic group of cycads which thrive in sandy soils and are highly tolerant of salinity. Found in tropical and subtropical regions throughout the world their origins are clouded due to their ocean spanning dispersal mechanisms, though most botanists agree they fit into the family Zamiacea.
They are perennial, evergreen, and dioecious.
They have tall and erect, usually unbranched, cylindrical stems, and stems clad with persistent leaf bases.
Their leaves are simply pinnate, spirally arranged, and interspersed with cataphylls. The leaflets are sometimes dichotomously divided. The leaflets occur with several sub-parallel, dichotomously-branching longitudinal veins; they lack a mid rib. Stomata occur either on both surfaces or undersurface only.
These traits however, are not what characterize the seacad. They produce drift seeds.
The seeds and the expanded thickened lamina (the outer part of the cone; the lighter brown bit) of the the seacad are highly buoyant and sealed against seawater. This allows them to disperse over staggering distances using ocean currents.
Seeing that the best chance for the seed to grow to maturity is to colonise a new beach the seed will sit in the cone of the parent plant until a rain event or storm when they have the best chance of being washed out to sea. When the lamina are wetted, they swell up and this sudden increase in volume pops them from the cone to be washed down the beach and out to sea.
As they are diecious (having seperate male and female plants seperate) the male and female seeds alternate spirally throughout the cone, assuring where there are two seeds attached to a lamina they will be able to reproduce should they both germinate on some foreign shore.
They grow best in partial shade. If you’ve read through this far then you are a very special person indeed.
If you enjoy speculative biology and evolution, you should check out this forum. Lots of great people with unique ideas. Also the competitions are pretty fun. Be sure to vote for my entries in the competitions if you do sign up, it would be muchly appreciated.



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