The ferns of Lord Howe Island

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Two Te Papa botanists recently spent a week collecting ferns on Lord Howe Island. They were adeptly guided by Lord Howe Island museum curator Ian Hutton and joined by Daniel Ohlsen from the Royal Botanic Gardens Victoria. The natural history of Lord Howe Island was introduced in an earlier blog post. Here, Leon Perrie and Lara Shepherd provide an overview of its ferns.

Our research programme investigating the relationships and naming of Aotearoa New Zealand’s ferns depends on also understanding the ferns of the surrounding landmasses.  Our Australian colleagues have a corresponding perspective; hence the trans-Tasman collaboration.

Looking up at a rocky mountain. The view is framed by fern fronds in the foreground.
Looking up at Mount Lidgbird. We later found a new record for the island on its slopes – see below. Photo by Leon Perrie. Te Papa

Our visit to Lord Howe Island follows a trip earlier in the year to Norfolk Island, some 900 km to the north-east of Lord Howe Island. Despite its smaller area, Lord Howe Island has more ferns, nearly 60 species, than Norfolk Island (about 45 species). This reflects Lord Howe Island’s greater elevation and it being closer to Australia.

Two photos side-by-side, with the same two men in each. In the first photo they are looking at ferns in a forest, in the second photo they are looking at samples of ferns on a table.
Leon (at left in both images) and Daniel; in the left image, with Psilotum nudum and Platycerium bifurcatum; in the right image, processing collections in the Lord Howe Island Board’s research facility.  Photos by Lara Shepherd. Te Papa.

Taxonomic questions

Several species are of particular interest regarding how they are related to populations and species of surrounding landmasses. We will test their relationships with DNA sequencing analyses.

A split photo with one third showing a fern leaf in full, and the other two thirds showing a close up of the underside of the leaves.
Asplenium polyodon.  Our earlier DNA sequencing work has shown that there are multiple species under the name Asplenium polyodon. From their appearance, we suspect Lord Howe Island plants are related to Australian and New Caledonian plants rather than those in New Zealand. Photos by Leon Perrie. Te Papa
The end of a fern frond with small yellow flowers and curled leaves coming off the central stem.
Hymenophyllum howense. Regarded as a species found only on Lord Howe Island, we want to test to what extent it is distinguishable from Hymenophyllum multifidum of New Zealand. Photo by Leon Perrie. Te Papa
A split image with one half looking at the underside off leaves growing out of a tree trunk, and the second half showing the tops of the leaves dropping down the length of the image.
Grammitis diminuta at left; Grammitis pulchella at right. Lord Howe Island is home to three grammitid ferns, all found only there. We want to test how they are related to other species, including the Notogrammitis species of Australasia. Photos by Leon Perrie. Te Papa
A split photo with one half showing a fern frond and the other half showing a closeup of the underside of one of the leaves and the spores.
Lastreopsis nephrodioides. It’s uncertain whether this endemic species belongs in Lastreopsis or the recently segregated Parapolystichum. The two genera are difficult to distinguish by appearances alone. Photos by Leon Perrie. Te Papa
A split photo with one half showing the roots and bulbs of a plant pulled out of the earth and the second half showing the leaves from the plant.
Nephrolepis cordifolia at left; putative Nephrolepis flexuosa at right. These two otherwise very similar species are distinguished by N. cordifolia having spherical tubers on its roots. Plants on Lord Howe Island have been previously recognised as N. cordifolia, but the New Zealand species N. flexuosa may also be present and be the appropriate name for indigenous plants.  Photos by Leon Perrie. Te Papa

Ferns endemic to Lord Howe Island

A notable feature of the fern flora of Lord Howe Island is the high proportion of endemic species. Some 25 are found nowhere else, including four species of tree ferns. Many of the endemic species are confined to Mounts Gower and Lidgbird.

A split photo with the first two-thirds showing a plant with broad green leaves growing out of the ground and the last third showing detail of one of the leaves.
Asplenium goudeyi. Distinguished from other birds nest ferns by the slightly narrowed ‘waist’ just above base of the leafy part of the frond. Photos by Leon Perrie. Te Papa
A photo of a wide fern frond with many leaves coming out of the central stalk.
Asplenium milnei. Common in many lowland forests. It has once-divided fronds like Asplenium oblongifolium of New Zealand and A. oligolepidum of New Caledonia but they are not immediate relatives. Photo by Leon Perrie. Te Papa
A top-down view of a fern with scraggly fronds coming from the centre with brown fronds in the middle.
Blechnum fullagarii. Related to Blechnum nigrum of New Zealand, but bigger and not as dark.  Photo by Leon Perrie. Te Papa
A split photo with one half showing a fern leaf and the other half showing detail of the underside of a leaf where it attaches itself to the stalk.
Blechnum howeanum. Similar to Blechnum novae-zelandiae and other kiokio ferns. Photos by Leon Perrie. Te Papa
A split photo with one half looking up under a tall tree fern and the second half showing an extreme close up of a stem of one of the fronds and the underside leaf.
Cyathea robusta. Similar to mamaku, Cyathea medullaris of New Zealand and some Pacific Islands, and Australia’s C. cooperi.  One of four endemic tree ferns on Lord Howe Island. Photos by Leon Perrie. Te Papa
A split photo with one half showing a fern frond and the other half showing a closeup of the underside of one of the leaves and the spores.
Diplazium melanochlamys. The frond has a slightly succulent texture. The species epithet references the dark indusia protecting the reproductive structures on the underside of its fronds. Photos by Leon Perrie. Te Papa
A large fern frond growing down towards the ground.
Leptopteris moorei. Part of a small group of species found mostly in Australasia. New Zealand representatives are heruheru, crepe fern, Leptopteris hymenophylloides and ngutu kākāriki, Prince of Wales feathers fern, L. superba. Photo by Leon Perrie. Te Papa
A split photo with one half showing a fern frond and the other half showing a closeup of the underside of one of the leaves and the spores.
Polystichum whiteleggei. A strikingly attractive fern, notable for its large indusia providing shield-like protection to its reproductive structures on the underside of its fronds. Photos by Leon Perrie. Te Papa
A split photo with two-thirds showing a fern frond and the other third showing a closeup of the underside of one of the leaves and the spores.
Pteris microptera. Part of the Pteris comans complex of species. Photos by Leon Perrie. Te Papa
Looking down on some fern leaves spread out in different directions.
Ptisana howeana. A relative of para, king fern, Ptisana salicina of Norfolk Island and New Zealand, but more similar to P. attenuata of New Caledonia in having thrice-divided fronds.  Photo by Leon Perrie. Te Papa
A split image with three people looking at fern fronds in the first half and two fern fronds in the second half.
Microsorum pustulatum subsp. howense, aka Lecanopteris pustulata subsp. howensis, with, from left, Lara, Daniel, and Ian.  It was very interesting to see the locally endemic subspecies of kōwaowao, hound’s tongue fern (or kangaroo fern in Australia). Lord Howe Island plants grow noticeably bigger, and have little difference in lobe width between fertile and sterile fronds (as shown at right). This species and Asplenium milnei are the most common ferns in lowland forests.  Photos by Leon Perrie. Te Papa

Species shared with New Zealand

About 15 fern species on Lord Howe Island are also indigenous to New Zealand. Some additional examples are in the slideshow below, along with the lycophyte Phlegmariurus varius.

Arthropteris tenella. Photo by Leon Perrie. Te Papa
Cheilanthes distans. Photo by Leon Perrie. Te Papa
Phlegmariurus varius. Photo by Leon Perrie.Te Papa
Psilotum nudum. Photo by Leon Perrie. Te Papa
Pteris tremula. Photo by Leon Perrie. Te Papa

Ferns not shared with New Zealand

Lord Howe Island also shares several ferns with other places that are not in New Zealand, such as those in the following slideshow.

Blechnum contiguum. Also indigenous to New Caledonia. Photo by Leon Perrie. Te Papa
Blechnum patersonii. Also indigenous to mainland Australia. The most closely related species in New Zealand is peretao, Blechnum colensoi. Photo by Leon Perrie. Te Papa
Hypolepis elegans. Also indigenous to mainland Australia, Papua New Guinea, and several Pacific Islands. Photo by Leon Perrie. Te Papa
Pellaea falcata. Also indigenous to mainland Australia. New Zealand previously attributed to this species are now considered to be long-pinnuled forms of Pellaea rotundifolia. Photo by Leon Perrie. Te Papa
Platycerium bifurcatum. Also indigenous to mainland Australia. Common in places on Lord Howe Island, with large plants regularly on the ground, having fallen from their usual epiphytic perches. Photo by Leon Perrie. Te Papa
Trichomanes bauerianum. Also indigenous to Norfolk Island and other Pacific Islands. Photo by Leon Perrie. Te Papa

A new discovery

We found a population of Dennstaedtia ferns, presumably indigenous. This genus has not previously been recorded from Lord Howe Island.

A green fern frond growing in a forest.
A species of Dennstaedtia – a new find for Lord Howe Island. Photo by Leon Perrie. Te Papa

Conclusions

Lord Howe Island is a fascinating place. We were fortunate to have the opportunity to visit, and to have the support of the Lord Howe Island Board. We’re particularly grateful for the guidance of Ian Hutton.

We look forward to sharing our results.

A photo of the back of a person carrying large fern fronds in a forest.
Lara with a haul of big ferns, collected within a short walk of the vehicle. Photo by Leon Perrie. Te Papa

 

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1 Comment

  1. Very interesting Leon.

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