The adaptability of New Zealand plants

By Alina Suchanski

Reading time: 8 minutes

New Zealand plants are unique. Scientists say that many of our native species are very similar to those growing on Earth in the time of the dinosaurs. Alina Suchanski explains why and gives some examples of how plants have adapted to Aotearoa’s environmental conditions.

New Zealand and Australia separated from the supercontinent of Gondwanaland 85 million years ago. Another 30 million years on, New Zealand drifted away from Australia to become a small archipelago – later named Aotearoa by the Māori settlers - tucked away from the rest of the world, halfway between Australia and Antarctica. It was this isolation that led to the emergence of New Zealand’s unique flora and fauna. We have some of the oldest primeval forests in the world and some of the largest tree ferns and fuchsias found anywhere.

By Alina Suchanski

Reading time: 8 minutes

New Zealand plants are unique. Scientists say that many of our native species are very similar to those growing on Earth in the time of the dinosaurs. Alina Suchanski explains why and gives some examples of how plants have adapted to Aotearoa’s environmental conditions.

New Zealand and Australia separated from the supercontinent of Gondwanaland 85 million years ago. Another 30 million years on, New Zealand drifted away from Australia to become a small archipelago – later named Aotearoa by the Māori settlers – tucked away from the rest of the world, halfway between Australia and Antarctica. It was this isolation that led to the emergence of New Zealand’s unique flora and fauna. We have some of the oldest primeval forests in the world and some of the largest tree ferns and fuchsias found anywhere.

New Zealand is a young country, populated by humans relatively recently. According to Te Ara – the Encyclopaedia of New Zealand, “people first arrived in Aotearoa around 1250–1300 CE, coming from East Polynesia in canoes”. Before human settlers started bringing in plants from their native lands, New Zealand flora evolved over millions of years without any competition from introduced species. Scientists estimate that 82% of New Zealand plants are endemic – they are not found anywhere else in the world.

New Zealand did not undergo the extreme ice ages of the northern hemisphere and because of the country’s mild climate, a vast majority of its native plants are evergreen, as there was no need for the trees to lose their leaves and hibernate over winter.

There are only 11 deciduous native New Zealand trees. One of them is tree fuchsia (kōtukutuku), a strong, almost indestructible tree but with soft, delicate leaves which may be the reason why the tree loses them in winter. It is the world’s largest fuchsia reaching up to 15 metres in height and is commonly found throughout New Zealand from sea level up to about 1000m, particularly alongside creeks and rivers. It is easily recognised by the characteristic appearance of its bark which peels spontaneously, hanging in papery strips to show a pale bark underneath. Kōtukutuku berries, known as kōnini, were used by the Māori people and early European settlers of New Zealand for eating and making jams.

Before being introduced by humans, there were no native mammalian browsers in this country, although there were moa – large herbivorous birds. One theory suggests it was to protect themselves from the moa, that lancewood (or horoeka), developed tough, lance-like leaves that point downwards. The ‘spines’ of young leaves are so strong and supple that European settlers used them as bootlaces. As the tree matures the leaves become smaller, softer and point up towards the sky. The idea that lancewood evolved in response to moa browsing indicated that once trees grew above what used to be moa height, they no longer needed the special defences of their juvenile leaves.

Many coprosmas have small leaves hidden inside a tangle of branches and bright berries to attract birds that spread their seeds around

Another case of adaptation specific to New Zealand is a characteristic growth form called divarication, displayed by many native shrubs such as coprosmas and matagouri. This is where the plant grows in a tangled way, with interlaced stems and small leaves. There are several ideas about why this is useful, but the dominant theory is that divarication may be a protective mechanism. The leaves are tucked inside and were therefore unattractive and less accessible for browsing moa, and less prone to damage from frost or snow.

Discaria toumatou, commonly called matagouri, is a tangle-branched thorny plant endemic to New Zealand. The name matagouri is an anglicized pronunciation of the Māori name matakoura and is also known as tūmatakuru. Matagouri developed nasty sharp thorns to deter animals from eating their leaves.

Ever wondered why New Zealand native flowers and blossoms are usually white? This is due to a shortage of butterflies and bees in this country. Our native plants are often pollinated by moths – nocturnal insects by nature, and because white is the most visible colour at night, plants evolved to attract moths with this colour.

Drosera arcturid, one of New Zealand’s alpine species of sundew – a perennial, insectivorous herb

We also have a few endemic carnivorous plants in Aotearoa. These are species that derive some or most of their nutrients from trapping and consuming animals, typically insects. Carnivorous plants have adapted to grow in places where the soil is thin or poor in nutrients, especially nitrogen; such as acidic bogs, tarns, and seepages, and most commonly in the mountains. An example is Drosera arcturid, one of New Zealand’s two alpine species of sundew – a perennial, insectivorous herb. It is found in alpine areas from the East Cape of the North Island, southwards to Stewart Island. This nifty little plant catches insects using sticky, glandular hairs on its leaves.

New Zealand has 2,363 species of indigenous plants. Of these, over 30% are threatened or uncommon. European settlers introduced many plant species that have become weeds and can either outcompete our native plants for habitat (wilding pines) or have a direct negative impact on the plants themselves by smothering them and cutting off the sunlight (as the old man’s beard does) and/or depleting them of water and nutrient supply. Also, insects may go for the nectar of the invading plant rather than the host, therefore affecting pollination.

Introduced predators can destroy pollinators such as insects or birds or impact negatively on the plants themselves, for example, mice eating native seeds. Possums can strip trees of their new growth, which can lead to trees dying.

In order to preserve the biodiversity of our country’s flora for ourselves and for generations to come, it’s paramount to protect and look after our unique species.

 

Photos: Alina Suchanski

Sources: 1. ‘When was New Zealand first settled?’, Te Ara – the Encyclopaedia of New Zealand 2. Fuchsia excorticata, Wikipedia 3. Lancewood/horoeka, n.d., Department of Conservation 4. Carnivorous Plants, The New Zealand Plant Conservation Network 5. Matagouri, iNaturalistNZ

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