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Saving the genes of one of Australia’s rarest eucalypts

morrisbyi 1

Dean Williams (Forestry Tasmania) inspects the capsule crop on trees grown from seed that was initially collected from from the dying Risdon Hills population of E. morrisbyi.(Photo: Brad Potts)

­morrisbyi 2

Collecting capsules from E. morrisbyi growing in the trial at Forestry Tasmania’s seed orchard facility near Geeveston. (Photo: Paul Tilyard).

Brad Potts
University of Tasmania

The Tas­manian endemic, Eucalyptus morrisbyi, is one of Australia’s rarest eucalypt species. It is naturally confined to just three small populations in Tasmania, near Hobart (Wiltshire et al. 1991). Despite being protected in the East Risdon Flora Reserve, the second smallest population has undergone dramatic decline in the last 20 years.  In the mid 1980’s there were 16 mature trees in this population but despite being protected from the wild-fires which have occurred in this area, most of these trees are now dead and the population mainly comprises immature coppice re-sprouts, a large proportion of which are in poor health.  This population has been shown to be genetically distinct - in both molecular makers (Jones et al. 2005) and leaf traits, including resistance to marsupial herbivory (Mann et al. in prep) - from the main population of E. morrisbyi that comprises about 2000 mature trees.

In 1983, 1989 and 1999, staff from the School of Plant Science (UTAS) have collected seed from reproductive individuals from the E. morrisbyi population at Risdon Hills as it declined. In collaboration with Forestry Tasmania and the Department of Primary Industries and Water’s Threatened Species Unit, two progeny trials were established in 1999. One was established in Forestry Tasmania’s multi-species seed orchard facility near Geeveston, and the other on an industrial site in Hobart belonging to  Pasminco E.Z. Pty. Ltd. (now Nyrstar Pty. Ltd).  These field trials were designed to compare seed lots from the small Risdon Hills population with those from the large Calvert's Hill population, but also provide a conservation planting and a source of future seed.  Approximately 30 seed lots were available from each population for planting at each site.

At the Geeveston site, heavy browsing over many years of the trees from the large Calverts Hill population, but less browsing of trees from the small Risdon Hills population, has meant that the first flowering in this E. morrisbyi planting was virtually confined to trees originating from the Risdon Hills population.  This has allowed seed to be collected that should be a virtually pure representation of the population that is at risk of extinction. In collaboration with Forestry Tasmania, the DPIW's Threatened Species Unit and the Tasmanian Seed Conservation Centre, we recently collected seed from this flowering from nearly 30 trees from the  population in this trial.  As there is the possibility of contamination of the seed from hybridisation with other nearby eucalypts, the seed will be tested for purity and then deposited for long-term storage at the Tasmanian Seed Conservation Centre which is part of the Millenium Seed Bank Project.