The lunar cycle is iconic for many cultures around the world. Long before it became part of the human lexicon, ecological systems were syncing up with Earth's rocky satellite. Everything from corals to moths have honed in on the moon's dominance in the night sky. Even plants utilize its reflective properties to their advantage. One must only marvel at the bright white blooms of a ghost orchid or Selenicereus cacti to understand what I am talking about. It's not just angiosperms that are taking advantage of moonlight either. As it turns out, at least one gymnosperm is also part of the lunar party.
Anyone who is aware of diet fads will have undoubtedly heard of Ephedra. These oddball gymnosperms are more familiar for the alkaloids that they produce than their ecology but one species is changing that. Ephedra foeminea is native to the Mediterranean region and has long baffled ecologist who study it. The odd thing about E. foeminea is that it is one of the few gymnosperms alive today that have evolved an insect pollination syndrome. Most other members of this genus are wind pollinated.
When E. foeminea becomes receptive for pollination, the tips of both male and female cones exude small droplets of a clear fluid. This fluid serves to aid in receiving and transporting pollen on insect bodies. However, with no discernible scent, it is hasn't always been clear exactly how insects locate the plants. That is, until recently. For years, researcher Catarina Rydin and her students have had trouble timing their field work around when these plants become receptive. Unlike some of its relatives, E. foeminea didn't appear to have a set reproductive schedule.
Then in 2014, Rydin realized something. After looking through photos of previous years, she noticed that the images in which the plants were exuding droplets were all taken on clear nights under a full moon. This was the missing piece of the puzzle. As it turns out, E. foeminea times its reproductive efforts around the full moon. Why?
Its actually quite simple. Without flowers or a scent, E. foeminea needs another way for insects to locate its cones. This is where the fluid comes in. Under the light of a full moon, the droplets cause the plant to sparkle. On a clear night, it would be hard to miss. Insects, specifically small flies and moths, have no issue tuning into this light display and thus the plant gets what it needs.
The question of how exactly it syncs up with the lunar cycle is a complete mystery. It has been suggested that perhaps the light reflected by the moon is enough to trigger some sort of light receptive chemical in the plant. I have also seen it proposed that the plants can detect the same changes in gravity that cause the tides, however, more work is needed to figure that out. Still others have suggested that these observations do not provide sufficient evidence that lunar cycles have any effect on E. foeminea whatsoever. Until more work is done, this intriguing reproductive strategy remains a bit in the dark.