More than 9 million years separate Australian and New Zealand mānuka

A study conducted by geneticists at Plant & Food Research has analysed the DNA sequence of mānuka trees (Leptospermum scoparium) from across New Zealand and Tasmania. The research identified nine family clusters in New Zealand, corresponding with different geographic regions, and two clusters in Tasmania. The New Zealand clusters were more closely related than those found in Australia, with evidence of recent cross breeding. The genetic differences between the clusters suggest that New Zealand and Australian mānuka diverged 9-12 million years ago.

“Genetic testing of mānuka previously had shown that there was a difference between those trees in New Zealand and those in Australia, so we wanted to understand more about the extent of these differences,” says Dr David Chagné. “Analysing more than 2,000 points across the genome showed a clear separation between the two countries, with more than 9 million years since there was any real crossover between them. Whilst there are several distinct clusters in New Zealand, these have the normal genetic spread you’d expect from families spread across a wide geographic area. The two Australian clusters, while related to each other, are vastly different, and could potentially be genetically classified as different species.”

The study – which builds on an earlier analysis of New Zealand and Australian mānuka led by Manaaki Whenua Landcare Research and published in 2022 - analysed 86 samples of mānuka from 7 locations across Tasmania and 458 samples from 22 locations across New Zealand. Using 2,069 SNPs (single nucleotide polymorphisms) across the mānuka genome, the team developed DNA profiles for each of the samples. Analysis of these profiles identified 11 unique clusters of genetically similar mānuka trees, nine related clusters from New Zealand and two from Tasmania.

The research was funded by Te Pitau Ltd, the operating arm of the Mānuka Charitable Trust, Plant & Food Research and the Department of Conservation. Mānuka samples were collected in New Zealand with permission from Māori landowners.

Mānuka, also known as tea tree, is native to New Zealand and southeast Australia, particularly Tasmania, Victoria and New South Wales. The tree was called mānuka by the New Zealand indigenous Māori.

Read the publication https://link.springer.com/article/10.1007/s11295-023-01606-w.