Fern  (Marattia purpurascens)

Classified as Near Threatened (NT) in 2003 under IUCN Red List categories (3).

This large fern has broad, sturdy fronds that can reach up to 1 metre in length (2). The dark green fronds are divided into as many as 3 branches, each with 6 pairs of leaflets, known as ‘pinnules’ (2). Ferns produce spores and these develop within structures known as ‘sori’, which line the edges of the pinnules (2).

Endemic to Ascension Island in the South Atlantic, this fern is today restricted to a single population on Green Mountain (3).

Marattia purpurascens is found growing in open grassland on the exposed side of Green Mountain and amongst bamboo thickets near to the summit (3).

Ferns are ‘primitive’ plants that spread by releasing spores rather than by producing flowers and fruits. The distinctive frond stage of the fern lifecycle is asexual; spores are released from the fronds, which then germinate into minuscule heart-shaped structures known as ‘prothalli’. It is here that the sexual stage of the lifecycle occurs; male and female organs on the prothallus produce sperm and eggs respectively. If the female eggs are fertilised successfully, a new fern plant will begin to grow and the cycle starts again (4).

The population of Marattia purpurascens is now believed to be more stable than was previously feared and the species has been downgraded to Near Threatened under IUCN categories (3). Long-term threats to its survival do exist however, in the form of competition with introduced species and grazing by sheep, although this is not currently a common occurrence (3).

Marattia purpurascens is the largest of Ascension Island’s native plants and its population is being monitored by Ascension Conservation (3).