Nematolepis wilsonii habitat (Image: Neville Walsh, Royal Botanic Gardens, Melbourne)
As well as the ever-present possibility of summer bush fires, one of the most serious threats to shining nematolepis is the sambar deer (Cervis unicolor). These deer are native to southern Asia (including India and Sri Lanka), and were introduced into south-eastern Australia in the 1860s by the Victorian Acclimatisation Society who sought to ‘improve’ the impoverished Victorian bush by adding species regarded as valuable for food, recreational hunting, or other resources such as timber. The past few decades have seen an explosion in sambar numbers and expansion of their range into new sites. While Nematolepis is not a favoured food-plant for sambar, their stems appear to offer just the right texture and resistance for the stags to ‘de-velvet’ their new antlers each spring, and in doing so they effectively ring-bark saplings and mature Nematolepis plants. They are preferentially sought out by sambar for this activity, and up to 10% of previously monitored individual plants had been killed or severely damaged by them prior to the fire, whereas plants of similar stature of other associated species remained untouched. Prior to the fires, about half of the population of Nematolepis had been fenced-in to protect them from deer.
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Prior to the 2009 fires, shining nematolepis was the subject of a translocation programme that sought to establish several new populations in secure sites nearby, in a separate sub-catchment of the Yarra River. Due to the same drought that caused February 2009 to be such a severe fire season, plants were not planted into their new homes (which incidentally and fortuitously were not burnt), but were maintained at the Royal Botanic Gardens, Melbourne and Royal Botanic Gardens, Cranbourne.
Like many capsular-fruited Rutaceae (tribe Boronieae), N. wilsonii initially proved difficult to germinate, so much of the material for translocation was grown from cuttings from 31 parent plants, sampled across the population to provide some genetic diversity in the founder population. Seedlings were not too uncommon in the wild – appearing at the edge of a small track that traversed the population, and on areas disturbed by mammals such as the native wombat (Vombatus ursinus), and the introduced sambar deer. Scientists found that the seeds needed time in the soil in nature, germinating after a suitable period following soil disturbance. Consequently, the translocation programme was designed to include seed addition near the plots where the nursery-grown plants were to be installed. It was hoped that, in time, plants produced in situ, would establish to create self-sustaining populations. Laboratory tests have now shown that N. wilsonii will germinate readily if exposed to a prolonged chilling (5˚C) period for 2 months. In nature, this corresponds to a winter dormancy and germination the following spring – a good strategy as spring is the season of maximum rainfall in the plants’ natural habitat.
