Botany curator Leon Perrie describes how a New Zealand fern’s closest relative has turned up in an unexpected place.
The Poor Knights spleenwort, Asplenium pauperequitum, was scientifically described in 1984, led by Te Papa’s Pat Brownsey. At the time, it was thought confined to its eponymous island group off the east coast of Northland. It has not been found on the North or South Islands, but the Poor Knights spleenwort was subsequently found on the Chatham Islands, some 1200 km away!
Because it has only small populations, it has a conservation status of Nationally Endangered.
Our DNA sequencing studies had shown that the Poor Knights spleenwort is not closely related to any of the other Asplenium species found in New Zealand, Australia, New Caledonia, or elsewhere in the Pacific.
So I was intrigued by a recent study (Xu et al. 2020, Cladistics 36: 22-71) that incidentally reported an unidentified sample collected from Borneo’s Mount Kinabalu as closely related to the Poor Knights spleenwort.
A distant connection
That Mount Kinabalu sample was collected by Cheng-Wei Chen. I knew Cheng-Wei from helping with his (excellent) book on the ferns of the Solomon Islands. He told me he had ruled out all spleenworts previously reported from Mount Kinabalu except for an unnamed species listed in a book by Barbara Parris.
Barbara is a New Zealander who was fern curator at the herbarium of Kew gardens. She has collected ferns on Mount Kinabalu among other places in south-east Asia.
I checked her specimens in the Kew collection, and with Barbara herself, and we confirmed that Barbara’s unnamed species was the same as Cheng-Wei’s specimen, for which DNA sequence data had been published.
Independently, Daniel Ohlsen found a specimen among the Papua New Guinean collections in the Canberra herbarium that resembled Asplenium pauperequitum. Guess what? Daniel’s find was the same species as Barbara and Cheng-Wei’s.
A new species
Putting this all together, Barbara, Cheng-Wei, Daniel, Pat and I formally described this species with a new scientific name, Asplenium alleniae. Compared with the Poor Knights spleenwort, Asplenium alleniae has larger fronds with fewer pairs of pinnae (frond segments), and the pinnae are longer and have more pointed ends.
Asplenium alleniae is known only from Mount Kinabalu on Borneo and Mount Giluwe on New Guinea, at elevations between 3160 and 3500 m.
We suggested it be regarded as Endangered because of its limited populations and because tropical mountain habitats are considered particularly susceptible to global warming.
Asplenium alleniae is named for Betty Molesworth Allen (1913–2002). She made the earliest scientific collection of the species that we know about. Betty spent most of her working career in south-east Asia, extensively collecting plants, particularly ferns, through Malaysia, Borneo, and Thailand. She was, however, born and brought up in New Zealand.
The scientific name of this species thus parallels the kinship link that this fern of tropical mountains in Borneo and New Guinea has with New Zealand.