'Zombie Tree' Faces Extinction Threat from Fungal Disease
A newly identified tree species, Rhodamnia zombi, also unofficially known as the 'zombie tree,' is at risk of extinction due to myrtle rust, a fungal disease. Found in the rainforests of Queensland's Burnett region, the species is experiencing significant decline, prompting scientists to initiate conservation efforts involving the propagation of cuttings and the search for disease resistance.
Species Identification: The 'Zombie Tree'
Rhodamnia zombi was initially assessed in 2020 and formally identified in research published in Austral Ecology. It is a small to medium-sized rainforest tree characterized by large, dark green leaves, flaky or shaggy bark, and white or hairy white flowers.
The Grave Threat of Myrtle Rust
The primary threat to Rhodamnia zombi is myrtle rust, a fungal disease that was first detected in Australia in 2010. This disease targets trees and shrubs within the Myrtaceae family, including Rhodamnia zombi. Myrtle rust attacks young shoots, preventing them from growing and reproducing, which can ultimately lead to the tree's decline and demise.
Botanist Rod Fensham from the University of Queensland, who served as lead author of the study, noted that since the initial assessment in 2020, approximately 10% of the Rhodamnia zombi trees have died.
The remaining wild population is reportedly not producing flowers or fruit due to the disease, leading scientists to describe the species as being in a "living dead" state.
Rhodamnia zombi is one of 17 species currently classified on a "Category X" list, indicating that none of them show apparent resistance to myrtle rust.
Without intervention, these species are projected to face extinction within a generation.
Urgent Conservation Efforts Underway
Despite the challenging outlook, conservation strategies are underway. Researchers note that some related species within the broader Rhodamnia genome exhibit natural tolerance to myrtle rust, offering potential hope for genetic resistance within Rhodamnia zombi.
The primary survival strategy involves collecting healthy, clean cuttings from wild populations before they become infected. These cuttings are then propagated in secure, controlled environments. Horticulturists, such as Alexandra Hayes-Hatten and conservation trainee Milo Wakeman-Bateman at organizations like Barung Landcare on the Sunshine Coast, are involved in collecting and cultivating these cuttings, trimming shoots, treating them with rooting hormone, and monitoring them for infection.
Specialist nurseries in locations including Lismore, Townsville, and Maleny are also contributing to these efforts. The objective is to cultivate these plants under protected conditions long enough for them to flower and produce seeds. The team aims to test subsequent generations for disease tolerance, with the hope that future generations of Rhodamnia zombi may develop and express resistance.
The long-term goal is to identify resistant individuals and eventually reintroduce them into Queensland’s rainforests, allowing them to develop natural defenses without constant fungal impact. This effort is recognized as both challenging and ambitious, requiring the trees to have time and space away from continuous exposure to myrtle rust to express any inherent resistance.