Eucalyptus Morrisbyi
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Eucalyptus morrisbyi morrisbys gum T A S M A N I A N T H R E A T E N E D S P E C I E S L I S T I N G S T A T E M E N T Image by Naomi Lawrence Scientific name: Eucalyptus morrisbyi Brett, Pap. & Proc. Roy. Soc. Tasmania 129: pl. 14–15 (1939) Common name: morrisbys gum Group: vascular plant, dicotyledon, family Myrtaceae Status: Threatened Species Protection Act 1995: endangered Environment Protection and Biodiversity Conservation Act 1999: Endangered Distribution Biogeographic origin: endemic to Tasmania Tasmanian Natural Resource Management Region: South Tasmanian IBRA bioregions (V6): South East Figure 1. Distribution of Eucalyptus morrisbyi, Plate 1. Eucalyptus morrisbyi: buds, capsules, adult & showing IBRA bioregions juvenile leaves (scale bar=2cm) (images by Brad Potts) Threatened Species Section – Department of Primary Industries, Parks, Water and Environment Listing Statement for Eucalyptus morrisbyi (morrisbys gum) SUMMARY: Eucalyptus morrisbyi (morrisbys gum) If flowering is compromised, the canopy held is a small tree endemic to Tasmania’s southeast. seedbank is only viable for about two years as It is only known from two locations 21 km capsules become too woody to release their apart; in the Government Hills near Risdon, seed. The Calverts Hill stand in particular has a and the fragmented Cremorne subpopulation large number of seedlings that have been which now consists of a main stand at Calverts repressed by continuous browsing to ground Hill and several small remnant stands following level and potentially may be many years old. past clearing for residential and agricultural Plants in the Risdon stand have resprouted purposes. The Risdon and the main Calverts from lignotubers following a major dieback Hill stands have suffered rapid dramatic event and genetic testing of stems has declines in recent decades with the loss of all demonstrated considerable clonality in the but a few mature trees which are all located at stand (Jones et al. 2005). Calverts Hill. The Risdon stand is now considered to be functionally extinct as it no Eucalyptus morrisbyi is susceptible to drought, longer produces seed. This leaves the species being the first of the local eucalypts to show with fewer than 30 mature trees in the wild that signs of stress following drought events, with produce seed. The species appears to have been stress symptoms particularly evident in trees contracting to wetter gullies over time, growing on drier sites. Stressed plants including exacerbated by the recent warmer and drier any regrowth are more susceptible to vertebrate conditions associated with climate change. The and insect browsing, often rapidly resulting in species is highly palatable and once stressed, death or dieback. recovery is hampered by vertebrate and insect browsing that if left unchecked leads to the There are considerable genetic differences death of trees within years. The smaller between the Calverts Hill and Risdon stands. roadside stands in the Cremorne area are Plants from the Risdon stand are less palatable additionally at risk from clearing to improve to vertebrate browsing as demonstrated in road safety and the small Lumeah Point stand mixed plantings (Mann et al. 2012). However, cannot expand due to existing urban plants from the Risdon stand have been shown development. While at imminent risk of to be more susceptible to myrtle rust extinction in the wild, the species is not likely to (Austropuccinia psidii) (newly introduced to face extinction in the short to medium term due Tasmania) than those from Calverts Hill (Potts to ornamental and ex situ plantings. The most et al. 2016). immediate needs are to protect wild and planted seedlings at Calverts Hill to allow them Plants from the two stands can be distinguished to reach maturity and to ensure that the genetic using molecular techniques (Jones et al. 2005). variability of the species is maintained by Some molecular differences are also evident supplementing and managing seed collections between plants from the Calverts Hill stand and that can be used for future conservation its associated remnant stands in the Cremorne actions. area. Despite the small size of the Risdon IDENTIFICATION AND ECOLOGY subpopulation, variation remains high and it is not showing signs of inbreeding. This may be a Eucalyptus morrisbyi is a small tree, growing to a consequence of inbreeding being limited by the height of approximately 6 to 12 m. Seedlings high levels of self-incompatibility shown by the take about ten years to produce flowers, a species (Potts & Savva 1988) and the longevity relatively long time for eucalypts. Peak of the existing genotypes. flowering occurs from February to May (Williams and Potts 1996). The species is Although Eucalyptus morrisbyi hybridises with relatively well adapted to fire, which stimulates Eucalyptus viminalis in the wild, studies have not release of seed from capsules for regeneration. revealed significant contamination of its gene pool. Threatened Species Section – Department of Primary Industries, Parks, Water and Environment 2 Listing Statement for Eucalyptus morrisbyi (morrisbys gum) Description A number of conservation plantings have been While Eucalyptus morrisbyi is generally rough made and Eucalyptus morrisbyi has been widely barked at the base of the trunk, the old bark is planted as a specimen tree and ornamental. shed further up leaving the upper part of the In natural stands, Eucalyptus morrisbyi occurs in trunk and the branches smooth and brown, coastal, dry sclerophyll woodland on gentle to white-grey or pink-grey in colour. The bluish- hilly slopes where it tends to be restricted to green juvenile leaves are glaucous, unstalked gullies that offer some relief in this drought and rounded, 2 to 3 cm long and 2 to 4 cm prone, low rainfall area. It is associated with wide. They are arranged in opposite pairs. The poor soils, with the Calverts Hill and associated adult leaves are stalked, less glaucous and remnant stands occurring on recent sands arranged alternately. They are about 5 to 10 cm overlying dolerite and the Risdon stand on long and 1.5 to 4 cm wide. The flower buds Permian mudstone. The species tends to occur have a pointed cap and are glaucous and shortly in relatively pure stands with a number of other stalked. They arise in clusters of three from the eucalypt species occurring nearby. leaf axils. The flowers are cream and develop into cylindrical, glaucous, woody capsules, 9 to 11 mm long and 6 mm wide (Plate 1). RESERVATION STATUS [description based on Curtis & Morris 1975] Eucalyptus morrisbyi is formally protected in the Calverts Hill Nature Reserve and the East Survey techniques Risdon State Reserve. The Lumeah Point stand is on a coastal reserve that has been leased to This small tree can be identified at any time of the Clarence City Council for recreational use. the year, though mature trees (with capsules) are required to confirm the identity of this POPULATION PARAMETERS species. Number of subpopulations: 2 (1 reproductive) Confusing Species Number of locations: 2 (1 reproductive) 2 Eucalyptus morrisbyi can be confused with the Extent of occurrence: ~45 km closely related Eucalyptus gunnii (cider gum), and Area of occupancy: ~ 12.5 ha Eucalyptus cordata (heart leaved silver gum). It (0.5 ha for mature individuals) Area of occupancy (as per IUCN criteria): 8 km2 can be distinguished from Eucalyptus gunnii by 2 its coastal lowland habitat and presence of (or 4 km as reproductive in only 1 location) warty protuberances on buds and capsules. It No. of mature individuals: < 30 can be distinguished from Eucalyptus cordata by Eucalyptus morrisbyi is known only from two its smaller capsules that occur in the axils of subpopulations in the wild (Table 1). In the adult leaves only. Refer also to Wiltshire and Cremorne area, the subpopulation has been Potts (2007). Eucalyptus morrisbyi can hybridise fragmented into the Calverts Hill stand, and with Eucalyptus viminalis and some stands and several small remnant stands approximately older plantings contain a significant proportion 2 km away. The species is no longer present at of hybrid trees. The hybrids are readily some sites where it was collected in the past in distinguished by their narrower and less the Cremorne area. Numbers in the smaller glaucous juvenile leaves. remnant stands have been supplemented by plantings and other plantings in the area have DISTRIBUTION AND HABITAT been made. Eucalyptus morrisbyi is endemic to Tasmania with A census of trees in the Risdon subpopulation wild occurrences known only from the in 1996 showed 69 trees with adult foliage, Cremorne area, with a main stand at Calverts though less than 20 of these were carrying seed. Hill and several small nearby remnant stands, as This stand is now functionally extinct with only well as from a small subpopulation 21 km away weak, spindly, non-reproductive lignotuber in the Government Hills near Risdon (Figure 1, regrowth remaining. Table 1). Threatened Species Section – Department of Primary Industries, Parks, Water and Environment 3 Listing Statement for Eucalyptus morrisbyi (morrisbys gum) The Calverts Hill stand is close to being It qualifies as Critically Endangered using the functionally extinct. There were 1915 mature IUCN (World Conservation Union) Red List trees in the Calverts Hill stand in 1991 and only criteria given its restricted distribution, a greater seven mature trees were still alive in early 2018 than 80% decline observed in the number of (one dying) following a dramatic decline that mature individuals and fewer than 50 mature started after 2005 (and was first reported in individuals remaining in the wild. 2014 at which time 70 to 80% of mature trees Eucalyptus morrisbyi forest and woodland is listed had already died). Seed-bearing mature as a threatened vegetation community on individuals can still be found in the small schedules of the Nature Conservation Act 2002.