Conservation ecology, genetics and propagation of the threatened species Samadera bidwillii (Hook.f.) Oliv.

This study examined the population ecology, genetics and propagation methods of the native threatened Samadera bidwillii (Hook.f.) Oliv. This species, previously known as Quassia bidwillii, belongs to the Simaroubaceae (order: Sapindales). It has a narrow geographic range from Mackay to Gympie in Coastal Queensland, Australia. Plant communities of S. bidwillii occur in the margins of lowland rainforests, open forests and woodlands. Some of these habitats have been subjected to extensive clearance and disintegration, resulting in a major decline in the population of S. bidwillii in recent times. Samadera bidwillii is also found in the Callide coal mine area in Central Queensland, where its presence was recognised as a matter of national environmental significance under the EPBC Act and hence the species needs to be protected. Field trips were conducted in 2010 and 2011 to 16 sites harbouring populations of S. bidwillii in the Callide, Hervey Bay and Mary River areas. Habitat survey and genetic analysis were limited to 11 sites. Site areas ranged from 0.34 to 6.67 ha and were 6 to 554 m above mean sea level on steep to moderate inclines mostly on southern slopes. The greater part of the habitat was dominated by tall open woodland and open to mid dense microphyll vine forest. Other genera such as Eucalyptus, Acacia, Boronia, Carissa, and Grevillea, along with the weed species Asparagus africanus and Panicum maximum were found across the sites. Soil pH and EC ranged from 4.4 to 5.4 and 0.031 to 0.116 ds M-1, respectively. Soil nutrients levels fluctuated across the sites, but overall Hervey Bay region was found having nutritious soils. Plant height and stem diameter varied significantly across populations and averages ranged from 68–309 cm and 7–33 mm, respectively. Fruiting was not observed at Callide mine populations but all other sites exhibited abundant fruiting. Threats to the species included habitat fragmentation, s, land clearing and mining, and the frequency of fire regimes. Population, growing in the dense tall forest was observed to have high flowering and fruiting, along with the least insect damage and minimal natural threats. A total of 10 polymorphic microsatellite markers for S. bidwillii were designed and successfully used in population genetic studies. These markers have been deposited in GenBank to provide substantial sequencing data for future studies. Population-level genetic analysis using these microsatellite markers revealed that S. bidwillii exhibited a low level of genetic diversity (A= 1.83, AE= 1.29; HE= 0.16 and %P= 57.3). Genetic differentiation among regions was found to be high, with high correlations between geographic and genetic distance. Bayesian cluster analyses identified three distinct genetic clusters, which divided the population of Callide, Hervey Bay and Mary River regions. Except for one population from Hervey Bay region (H2), no other population of S. bidwillii evidenced genetic bottleneck. Population density, altitude and slope correlated with genetic diversity of the species. Germination and propagation studies conducted using seeds and root cuttings resulted in successful reproduction of S. bidwillii. A total of 66% seeds found viable and 53% seeds latter germinated which were collected in summer (January). For plants propagated by root cuttings, 5 cm long cuttings treated with 8 g L-1 IBA hormone resulted in 66.7% success. The results of this research have provided a framework for the development of species-specific conservation and restoration strategies for S. bidwillii. The Callide mine populations should be treated with care while selecting propagation materials, due to the distinct genetic structure with lack of allelic diversity and the presence of private alleles. Recovery measures such as protection, monitoring and management of the habitats containing S. bidwillii populations, along with associated adjacent ecosystems are critical. It is also essential (a) to conduct long-term site-specific ecological studies, (b) to preserve considerable populations in large reserves, (c) to collect seeds from as many plants as feasible to maintain levels of genetic diversity and (d) to implement effective programs of fire and pest management. e reserves, (c) to collect seeds from as many plants as feasible to maintain levels of genetic diversity and (d) to implement effective programs of fire and pest management.