Dragons in the mist

We can gain an understanding of New Zealand’s ancient past by studying our plants and their distribution.

This enables us to find answers to questions such as:

• where do they come from?
• how long have they been in New Zealand?
• how often and when did they disperse from New Zealand to neighbouring islands or continents?

Dr. Steve Wagstaff from Landcare Research recently undertook a project to try and understand the origins of a New Zealand genus, the Dracophyllum, which is a tree and shrub genus best known to New Zealanders as ‘turpentine scrub’, ‘pineapple scrub’, or ‘Dr Seuss trees’.

The name Dracophyllum means ‘dragon-leaves’ and comes from the resemblance of the leaves to those of the dragon-tree (Dracaena draco), a monocot tree of Central America that is like our cabbage trees (Cordyline) species.

During the study, Dr Wagstaff and his colleagues sampled Dracophyllum in the following countries: New Zealand, Australia (including Tasmania), New Caledonia and Lord Howe Island.

From analysing the DNA from these plants, the early results indicate that the Dracophyllum lineage is about 20 million years old. It then dispersed from Australia to New Caledonia about 7.7 million years ago.

However, Dr Wagstaff’s hunch is that Dracophyllum did not reach New Zealand until about 2.2 million years ago. That was at the beginning of the Pleistocene era when the mountains in New Zealand were starting to uplift, and the glaciations of that era also began. And at that time the Australian climate was becoming much drier and wetter mountain habits were forming in New Zealand.

One of the interesting results from the study is the importance of not studying New Zealand’s plants in isolation.

We can make incorrect interpretations of the New Zealand flora if we study it in isolation. The regional context allows us to appreciate how unique our flora is, but also how its history is strongly tied to the floras of nearby countries.

Dr Steve Wagstaff