John Hall and Gimme Walter of the University of Queensland have demonstrated that modern cycads and the original fossil cycads from 280 million years ago have adapted to survive by defying one of the basic plant evolutionary principles in the Aug. 20, 013, issue of the American Journal of Botany.
Cycads are one of the first seed bearing plants that arose during the Jurassic period. The plants are common in tropical and subtropical regions today.
Cycads are both male and female. The plants rely on insect pollination for reproduction. The seeds are large compared to other plant seeds.
Cycads exist in small cycad forests and have since the plants first appeared. This arrangement defies a basic assumption that large animals during prehistoric times would have consumed the seeds and spread them throughout larger areas. The broadcast of seeds over a large area is considered to be an advantage to survival.
The researchers tested the dispersal theory with an Australian cycad species Macrozamia miquelii. The fertilized seeds were tagged with bolts.
The researchers found that small animals moved the seed less than one meter from the seeds original position. No larger animals were involved in the seed dispersal.
Cycads have an evolutionary advantage in having large seeds that are not spread very far from the fertilized female. This fact defies the accepted assumptions that smaller seeds would have been an adaptation to promote cycad survival.
The discovery does not imply that large animals may have spread cycad seeds in prehistoric times.