Of New Zealand’s 194 native ferns and lycophytes, 90 species (46%) are endemic and 104 species (54%) also live in other countries:
- 95 in Australia
- 56 in the Pacific and the Malaysia–Indonesia region
- 15 in temperate South Africa
- 14 in the subantarctic islands and South America.
This distribution differs from that of New Zealand’s seed plants, which have a high degree of endemism – 84% are found nowhere else. It is likely that ferns and other spore-producing plants (such as mosses and liverworts) are more widespread because the lightweight spores are easily blown long distances by strong winds.
If New Zealand ferns and lycophytes are of recent origin, it is likely they were carried by westerly winds from Australia. However, anticyclones in the south Tasman Sea produce easterly winds from New Zealand to Australia, so it is possible that some ferns and lycophytes which evolved in New Zealand have been dispersed east to Australia.
Most endemic ferns and lycophytes live in the south, in cool rainforest. By contrast, those species shared with Australia and tropical countries are found mainly in northern New Zealand.
How did they get to New Zealand?
Ferns and lycophytes belong to ancient groups of plants with long fossil records, extending back some 410 million years in the case of lycophytes, and 380 million years for ferns.
There are two possible ways that native ferns and lycophytes arrived in New Zealand:
- They may have been on the New Zealand land mass when it split away from the supercontinent Gondwana about 85 million years ago.
- Their spores may have blown to New Zealand from populations on nearby land masses, and become established.
It was once thought that because New Zealand ferns and lycophytes belong to ancient groups of plants, they had a Gondwanan origin. However, this view is now being challenged. Evidence seems to suggest that most arrived as wind-blown spores in the intervening period since New Zealand separated from the supercontinent.
Weeds and invasive species
Some 35 ferns and lycophytes introduced to New Zealand are now established in the wild. A few have become weeds and some are potentially invasive. The most threatening are:
- African clubmoss (Selaginella kraussiana), which displaces native ferns, mosses and liverworts on stream banks in damp forest, and regenerates easily from fragments
- common horsetail (Equisetum arvense), an extremely invasive weed of open river banks
- male fern (Dryopteris filix-mas), an increasingly common weed in the South Island.