Rare endangered plant found in our Muriwai Beach area: Leptinella rotundata

The exceptionally rare Leptinella rotundata.

Muriwai's unique biodiversity takes another leap forward

Hot on the heals of the discovery of the Muriwai Gecko, in late December 2020, members of MEACT, who were out on a trap line servicing run, found a rare plant called Leptinella rotundata. It wasn’t a chance encounter, we had been looking for it for several months. The plant is rated nationally, critically threatened for the reasons explained below.

It’s not a spectacular plant to look at and it does blend in with the other plants that it grows amongst, but there are things about it which raise most intriguing questions. It’s not known for certain why it is in steady decline, and how it reproduces given that the plant colonies are of one sex only. But read on.

The following description of the plant’s history and future prospects is extracted from an article appearing in the New Zealand Plant Conservation Network’s newsletter of December 2014 entitled; “Leptinella rotundata—an enigmatic plant living life on the edge.

Often mistaken for Leptinella rotundata this is, in fact, Centella uniflora.

Leptinella rotundata, was originally discovered in 1906 in two localities in the coastal cliffs to the west of the Waitakere Ranges. Since that time 114 years ago, small colonies have been discovered in just eleven isolated patches on the west coast scattered between Bethells Beach at the southern limit and north up to Cape Reinga. The patches are mostly only one or two square metres in area and about half of these were discovered in the 1990’s and 2000’s after it was found that the known colonies of the time were becoming severely depleted. It is considered by the science community that this process is continuing and the question being asked is, why? The most compelling reason is the plant is short-lived, (just a few years), usually dying out from the centre of the colony. Other likely reasons are possum browsing, predation by plant collectors for gardens, coastal erosion, and crowding out and shading by quick-growing introduced shrubs and grasses. The pressures driving this plant species to extinction are not going away.

The other big question being asked is to do with their reproductive habits. With the fact that the plants are either male or female and the colonies are of one sex only, combined with large distances between colonies, it is not known how or whether these colonies reproduce sexually or can or will survive in the long term.

More work and research is being called for to answer these questions.

Our MEACT team found its colony in a rocky cliff-top area high above the sea at the top end of the Te Henga Walkway. The patch was only about one square meter and infested with dandelions. We were unable to tell whether our colony was male or female so, we will be visiting it regularly to check on it when it produces its ‘fruiting body’, called a capitula, and only then will we be able to tell its sex. According to the article the plant is found not only in rocky locations on the coast but also in sand dune habitats.

It is worth reading this salutary quote from the article:

“In the interim, Leptinella rotundata remains a seriously threatened species. Because it is short-lived and tends to die out centrally, it doesn’t seem to be widely cultivated. Ex-situ stocks therefore offer little in the long-term to secure this species. Understanding its autecology, supplemented by increasing our knowledge of its population genetics, in site and between site genetic variation, will. We hope this article will stimulate an interest to see such work done. In the meantime, there is also the hope that these notes will encourage other ‘westies’ out there to start looking, as we have shown, this plant may very well be in your west coast bach back yard, and why is it confined to west Northland? We suggest looking along the South Kaipara Beach, and along the western Manukau—western Waikato coastline.”

This is where we, in MEACT, ‘stepped up to the plate’ and found one of these colonies in our Muriwai area. The fact that we have seen for ourselves the actual plant, the kind of habitat that it grows in and the kind of plants that grow around it means that we can now keep a sharp eye out for it and have a much better chance of finding new colonies. We also now know what other plant species whose leaves are a similar shape and size are, (like the common Meuhlenbeckia) so we can quickly distinguish them from the real Leptinella.

Going forwards from here on we will be taking up the challenge to find other colonies – if they do indeed exist, with particular focus on the Auckland Council’s Five Mile Strip Reserve, (it’s called South Kaipara Beach in the article). There are also other sites that look promising in the bays to the south of Muriwai, the very area where our Muriwai Penguin Group has trap lines protecting Korora (Little blue penguin) nesting boxes and burrows and also Grey-faced petrel burrows.

The science community have confirmed our finding of Leptinella and expressed their appreciation. We, in MEACT, were chuffed to receive this acknowledgement. But apart from that, it is a neat feeling that we have living with us in our area yet another rare species making Muriwai a little bit special.

Here is the link to the article quoted above for more information; https://www.nzpcn.org.nz/publications/documents/trilepidea-e-newsletter-no-133-december-2014/. The pdf file can then be downloaded here.

If you want to join in the hunt for this rare species, try not to fall into the trap that we did when we mistook a similar looking, very common plant called Centella uniflora for Leptinella. It's no relation, it grows in a similar habitat and where we found our Leptinella colony, it was growing right in amongst it. Looking at the photo of it, it's in the centre, surrounded by another very common attractive coastal ground cover plant called Selliera radicans.

If you should find a patch of Leptinella rotundata, give us a call at MEACT, the science community would really value your discovery.

Find out more about Muriwai's unique environment.