Cracking the Code of Cycads

Botanists at the Northern Territory Herbarium have teamed up with the University of Edinburgh and California Academy of Sciences to crack the genetic code of Top End cycads.

Senior botanist Nick Cuff said ongoing research has raised doubts about the identity and distribution of Cycas armstrongii, a commonly seen Cycad in woodlands around Darwin.

Mr Cuff said it’s possible there might be more cycad species than previously thought.

“Cycads as a plant group have outlived the dinosaurs and the species we know as Cycas armstrongii can be found from Cobourg Peninsula and Tiwi Islands in the north, extending as far south as Litchfield National Park in the south,” Mr Cuff said.

Cycas armstrongii is named in honour of JF Armstrong, a botanical collector employed by Kew Gardens in the United Kingdom in the mid-19th Century.

“Armstrong collected the first specimens of the plant at Port Essington in 1838 where he was tasked with establishing a Government Garden at the newly established Victoria Settlement.

“These plant specimens were sent back to Europe where they were formally described and named by eminent Dutch botanist FAW Miquel but the exact location of where Armstrong collected his specimens was very uncertain.

“The NT plants were subsequently thought by George Bentham, another prominent botanist of the time, to be no different to a species from the east coast of Queensland, Cycas media.

“Interestingly, Cycas media was originally collected by Joseph Banks and Daniel Solander in 1770 as part of Captain Cook’s expedition and the NT Herbarium have a fragment of this original plant specimen in its Darwin collection.

“This remained the situation for more than 100 years until 1980 when NT Government botanist John Maconochie recognised the distinctive characters of the plants in the Top End and reinstated the original name Cycas armstrongii.  

“Research undertaken since the mid-1990s has suggested to NT Herbarium botanists that there were subtle morphological differences across the species range from Darwin to the Tiwi Islands and Cobourg Peninsula that warranted further investigation.

“However, this could result for a number of reasons including; natural variation within the species, actual differences between the populations (different species, sub-species or varieties) or possible hybridisation between Cycas armstrongii and one or more closely related cycad species found in the region, such as Cycas maconochiei.

“Cycads are unusual in that species are readily able to cross-pollinate in the wild if there is overlap in the time of flowering between species and pollinators such as beetles are active.

“These differences could not be easily resolved without relatively expensive genetic barcoding of the species.

“We were lucky to be able to collaborate with an international team working on Cycads and are sending specimens to the California Academy of Science for genetic sequencing using a range of newly-developed, sophisticated Next Generation techniques.

“These techniques characterise large parts of the genome and allow wider comparisons to be made between different populations or species to identify the differences, if any, between them.

“The DNA of the Cobourg Peninsula cycad population will be compared to the DNA from the other populations from around Darwin and Litchfield as part of this ground-breaking research.

“Researchers from the University of Edinburgh are supporting this research by working out what parts of the genetic code may be useful in identifying differences between species.

“Given the amount of data that the analyses produce, this requires use of a High Performance Computing (HPC) system (supercomputer) on which the sample results can be compared; even then the computer system takes about a week to process all the data.

“If the plants on the Cobourg Peninsula are genetically distinct from the Darwin region plants, this will mean the plants we are familiar with in the Darwin region are in fact a different species, sub species or variety and we look forward to receiving the results in June or July.

“The new, and old, species will require a new conservation assessment, with Cycas armstrongii currently classified as vulnerable in the Northern Territory.

“Further reports of cycads from the area from Traditional Owners are hoped to be followed up to help gain a better understanding of the distribution of these iconic but relatively poorly understood plants from the Top End.”

The California Academy of Sciences is a renowned scientific and educational institution dedicated to exploring, explaining and sustaining life on Earth, with more information available at www.calacademy.org

The University of Edinburgh is a world renowned tertiary institution with a strong research focus on the development and evolution of plants. More information is available at www.ed.ac.uk/biology/research

Go to https://nt.gov.au/environment/native-plants/native-plants-and-nt-herbarium for more information about the NT Herbarium.

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Last updated: 28 November 2017