Cycad Relations Run Hot and Cold

Cycads have an evolutionary history dating back to the dry, cool age of the Triassic, when much of the world’s terrestrial landscape was inhospitable to spore-producing plants. They have carried the evolutionary breakthrough of the seed from an ancient group of now-extinct plants called Bennettitaleans, to the present.

Cycads are pollinated mainly by weevils and thrips, which carry out much of their life cycle within the tissues of the male and female cones. In what could be considered an insightful adaptation to global warming (albeit at a micro-level), an ABC Science Online article by Stephen Pincock reveals how another species of cycad Macrozamia lucida uses a stockpile of sugars, starch and fats to heat their cones to around 12 degrees Celsius above air temperature to encourage thrips to evacuate to the more appealing climes of the female cones.

Whilst cycads are pollinated by weevils and thrips, the distribution of their seeds is reliant upon another group of animal carriers.

The world’s tallest cycad Lepidozamia hopeii can reach twenty-metres. Every five-years-or-so, female plants produce large cones that mature over about ten months. They then collapse and bright-red seeds adorn the forest floor at the base of the plant. Mammals carry individual seeds away from the intensity of competition and remove the delectable red aril from the seed, leaving the camouflaged core to recruit away from the competitive disinterests of the parent plant.