A new tree fern – or an unexpected hybrid?

A new tree fern – or an unexpected hybrid?

In 2015, ecologists Chris Stowe and Claire Newell found a strange fern during a vegetation survey in Whirinaki Forest, in the eastern North Island. They sent a frond to Te Papa’s fern experts Leon Perrie and Patrick Brownsey, who were also puzzled. This fern was clearly a Dicksonia tree fern but didn’t match any known species. Was it a new species?

Te Papa’s Leon Perrie and Lara Shepherd travelled to Whirinaki to see this strange fern and found about 80 individual plants.

These ferns had fronds like those of the trunkless stumpy tree fern (Dicksonia lanata) and a trunk like whekī-ponga (Dicksonia fibrosa).

(A) Whekī-ponga showing the trunk and skirt of dead fronds. (B) The strange Whirinaki fern with its trunk and less-developed skirt of dead fronds compared with whekī-ponga. (C) Stumpy tree fern with its lack of trunk. Photos by Leon Perrie. Te Papa

Genetic analysis of the ferns showed that they were not a new species. Instead they were hybrids between stumpy tree fern and whekī-ponga. This was an unexpected result because, unlike many other fern groups, Dicksonia ferns only rarely hybridise.

Even more interesting is that the two parent species are not even closely related to each other. They are thought to have diverged from each other 55 to 25 million years ago – yet they can still hybridise! For comparison, cattle and sheep are thought to have separated less than 20 million years ago.

Dicksonia tree fern spores. (A) Spores of whekī-ponga. (B) Spores of stumpy tree fern. (C) and (D) The spores of the strange Whirinaki ferns were abnormally formed, consistent with them being hybrids. Photos by Leon Perrie. Te Papa

This study has now been published:

Shepherd LD, Brownsey PB, Stowe C, Newell C, Perrie LR. 2019. Genetic and morphological identification of a recurrent Dicksonia tree fern hybrid in New Zealand. PLoS ONE

3 Comments

  1. Avatar

    Very interesting. Since at least 80 of theses ferns have happened, does that mean it is reproducing truly?

  2. Avatar

    Great work, Lara et al.

  3. Avatar

    What a fascinating discovery, and an interesting blog; thank you. This result certainly underlines the need to be observant and critical when looking at plants and animals.

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