Tapa, or barkcloth, is an important textile in the Pacific. Tapa is made from the beaten inner bark of some plant species, but once the tapa is made then identifying which plant species was used is difficult. Our genetics researcher Lara Shepherd teamed up with Catherine Smith from the University of Otago and colleagues to create a DNA reference database for identifying the plants used to make tapa.
Tapa was an important material in the Pacific before the 19th century but its production declined when European fabrics became readily available.
Given its portability, tapa was a popular souvenir for early European travellers. Consequently, there are many tapa artefacts in museums worldwide but information about their origins was not always recorded.
Identifying the plants used to make a particular tapa can help determine where it was made.
Round the mulberry bush
Most tapa in the Pacific was made from paper mulberry but a number of other species were also used including banyan fig, hibiscus and breadfruit. Māori brought paper mulberry with them to New Zealand but our cooler climate meant that the plants did not thrive.
However, tapa, known as aute in te reo Māori, was also made from some native New Zealand plants including houhere (lacebark) and autetaranga (sand daphne). There are no confirmed surviving examples of pre-European aute but the practice has been recently revived.
Methods to identify the plants used to make tapa, such as microscopy, have had limited success to date. Therefore, we decided to explore the use of DNA identification.
First, we made a list of all the plants used to make tapa, based on indigenous knowledge. We then made a reference library of DNA sequences by gathering published DNA sequences from these plants.
One particular piece of DNA had already been sequenced for many of the plants used for making tapa. We then sequenced the same fragment of DNA from as many of the plants that had not yet been sequenced as we could find.
Written in our DNA
Analysing our reference DNA library showed that the DNA sequences could identify most of the plants to genus.
Many of the species within a genus, such as the species of houhere (lacebark), could not be distinguished from one another. This is likely a result of hybridisation, which moves DNA between species.
However, identification to genus is still sufficient to determine the origins of some tapa, particularly those made from native plants from New Zealand and the Hawaiian Islands.
The second aim of our study was to compare different methods for extracting DNA from tapa. We examined a number of methods that have been used by other researchers that involve removing and destroying small pieces of the tapa (destructive methods).
We also tried several non-destructive methods but these were largely unsuccessful. However, we did determine the best destructive DNA extraction method, which will be useful for future studies.
We are now hoping to use both DNA and PLM microscopy methods to identify the plants in a collection of important pre-contact aute held at Otago Museum, which has long been thought to be made from endemic New Zealand plants.
Shepherd LD, Smith CA, Lowe BJ, Campbell D, Ngarimu R (2021) The identification of plants used to make tapa artefacts: development of a reference DNA database and trial of non-destructive DNA extraction methods. Journal of the Royal Society of New Zealand.