North Queensland Naturalist
North Queensland Naturalist 47 (2017): 56-64
The strange case of Queensland Peppermint (Eucalyptus exserta) on Dunk Island
Donald C. Franklin & Christine Sanders
In 1951, botanist Stanley Blake visited Dunk Island for a day, subsequently lodging 33 collections of 16 plant species from there with Australian herbaria. Among those collections are three of Eucalyptus exserta (Queensland Peppermint). This struck us as strange because Queensland Peppermint is a small tree in north Queensland otherwise associated with harsh woodland sites with 500 to 1,400 mm mean annual rainfall and a long dry season, whereas Dunk Island has a mean annual rainfall of 2,800 mm, a muted dry season and dense vegetation. Eucalypt specialists confirmed the correctness of Blake’s identification from his specimens and agreed that the location was quite out of character.
We visited Dunk Island twice to search for the species. On the second occasion we had the information that Blake’s specimens are labelled as being 4 m above sea level (no other specific location information being available), and found the species readily. On Dunk Island, Queensland Peppermint occurs along the walk to, and behind, Muggy Muggy Beach at the north end of the island along at least 850 m of coastline, and the population is likely to number several hundred mature individuals. Many are scarcely above the high-tide mark and overhang the sea, but others grow on the adjacent slope to about 40 m ASL. The species is associated there with jagged upturned outcrops of strongly-metamorphosed layered rocks that generate harsh growing conditions.
The occurrence of Queensland Peppermint on Dunk Island raises intriguing ecological and biogeographical questions.