Coprosma  (Coprosma wallii)

Classified as Vulnerable (VU) on the IUCN Red List (1).

Coprosma wallii is a densely branched, tree-like shrub that produces a multitude of distinctive, small, fleshy fruits. The fruits grow in fused pairs, and are green when immature, usually becoming purple when ripe (3) (4). The fruits sit directly on the branches, and contain hard-shelled pits with a pair of seeds inside (3). Coprosma wallii is an evergreen species (5), with dull green leaves that grow in small clusters (4) (6). The stems of this species are hairy when young (3), developing a layer of brown bark with age, below which the inner bark layer is an unmistakable orange colour (4).

Endemic to New Zealand, Coprosma wallii is known from just three locations on the North Island, and from Nelson, Westland and Canterbury on the South Island (1).

Coprosma wallii is found in fertile, lowland and montane areas where the climate is cool and dry. It typically grows along forest margins, flood plains and on elevated, flat plains where frosts may be experienced throughout the year (1) (2) (3).

A dioecious species,individual plants of Coprosma wallii bear either male or female flowers (2), which are wind pollinated (7). Fruits are produced throughout the year, and once fallen, the seeds quickly germinate, forming numerous seedlings around the parent plant (2). Other seeds are transported further afield by fruit-eating animals, such as birds, bats and lizards, which are attracted to the conspicuous, colourful fruits, and later pass the seeds in their droppings (5). In order to survive, seedlings require disturbed areas of soil, with high exposure to light, and are easily outcompeted by other plants. However, those individuals that do become well established may have a long-lifespan, possibly reaching over 100 years (2).

On the North Island the small, fragmented populations of Coprosma wallii are undergoing a gradual decline due to the presence of non-native plant species such as pasture grasses. These species rapidly outcompete Coprosma wallii, reducing areas of bare disturbed ground where seedlings can establish, and limiting light availability. In addition, many seedlings that do manage to become established are subsequently grazed by livestock (2). Although the populations of Coprosma wallii on the South Island are significantly larger, and more numerous, they are, nevertheless, highly fragmented and faced with the same problems (6). The ever-present risk of fire, as well as forest clearance for development and agriculture, are also significant threats to this species (8).

In order to mitigate threats to this vulnerable species, the New Zealand Department of Conservation (DOC) (2) has developed comprehensive management schemes such as the Plant Conservation Strategy for the Wellington Conservancy on the North Island. Through dedicated surveys and research into the ecology of Coprosma wallii, the DOC has highlighted key areas for conservation action, such as protection of existing populations by removing alien species, and by establishing cultivated stocks to ensure that wild populations can be replenished and are safeguarded against total extinction (2) (8).

To learn more about the New Zealand Department of Conservation’s work visit:

• Department of Conservation:
  www.doc.govt.nz