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It is now generally accepted that the southern hemisphere continents and the landmass of India were once part of a single southern continent called Gondwanaland.
This huge landmass straddled the South Pole during the Carboniferous and Permian periods. However, by the Triassic and Jurassic periods (230-150 million years ago) the New Zealand and Tasmanian landmasses had started to move away. The last links to Australia probably existed until the Cretaceous period (135-100 million years ago) by which time the Tasman Sea was opening up. By this time the ancestors of many of the plants now found in our podocarp forests were established on the landmass that was to become New Zealand.
During the Cretaceous period, Gondwanaland continued to break up with India and Africa drifting to the north, South America to the west and Australia, with its marginal islands of Tasmania, New Zealand and Papau New Guinea, drifting off to the east. Antarctica remained over the South Pole.
This process of continental drift largely explains the relationships between the plants that exist in New Zealand today and those in Australia, Tasmania, South America, Papua New Guinea and Indo-Malaysia.
New Zealand’s plants have developed in relative isolation for more than 60 million years. This has given a flora that is not rich in species of higher plants (which developed on the larger continents millions of years later) but vegetation which is special because a high proportion of species are found nowhere else - 85% of seed plants and 40% of ferns are endemic. About 75% of New Zealand’s seed plants and 85% of ferns are related to Australian genera. Similarly, 40% of New Zealand genera are shared with South America.
New Zealand’s podocarp rainforests have more species with ancient lineage than similar forests elsewhere and are amongst the most ancient forests in the world. The ancestry stretches back, without much modification, to the ancient forests of Gondwanaland.
Fossil pollen indicates that that precursors to some of New Zealand’s podocarp species existed 135-100 million years ago. The genus Dacrycarpus is represented in New Zealand by white pine, kahikatea (D.dacrydiodes). It appears to be the direct descendant of an earlier species Podocarpidites ohikaensis, suggesting a line of descent of more than 110 million years.
The ancestor of the kauri tree, Araucariacites australis, first appeared 190-135 million years ago and fossil material of kauri, Agathis australis, has been found dating from 100 million years ago.
Similar evidence of the lineage of beech forests also exists. Tracing back until at least the early Cretaceous, with distinct red and silver beech types being in evidence 65-100 million years ago.
The location of these species in New Zealand fluctuated during the Tertiary period with glaciations forcing the beech further north, while at other times the kauri has spread considerably further south.
Geological records also show that the Jurassic and Cretaceous periods were the era of the dinosaurs; emphasising the antiquity of New Zealand’s primordial forests.
So, in summary:
1. the plants of New Zealand have developed in relative
isolation for more than 60 million years.
2. New Zealand’s podocarp rainforests contain more
species with ancient lineage than similar forests
elsewhere.
3. Fossil pollen indicates that the precursors to some of
New Zealand’s podocarp species existed 135-100
million years ago.
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