Long-term monitoring of the threatened lesser guineaflower Hibbertia calycina (DC.) N.A.Wakef. (Dilleniaceae) in Tasmania

Abstract

This paper describes the distribution of the threatened shrub Hibbertia calycina (DC.) N.A.Wakef., a distinctive plant restricted to northeast Tasmania. It compares changes over time in population size and evaluates the species response to disturbance. Results found H. calycina distribution is restricted to isolated clumps on highly insolated ridges and steep upper slopes of fine-grained Mathinna-series sedimentary rocks in dry sclerophyll forest dominated by Eucalyptus sieberi L.Johnson. Nine populations were documented with an estimated area of occupancy of 0.43 km2 and area of extent measuring 95 km2, demonstrating that the current listing of H. calycina as vulnerable is appropriate on Tasmania’s Threatened Species Protection Act 1995. We believe that the distribution of the present population is a result of natural factors (i.e., restricted habitat range and natural fire events) and anthropogenic factors (managed fire regime and illegal firewood cutting). Although frequent fire and roading have the potential to impact populations, H. calycina appears to be stable without active management in a landscape of patchy, regular, low severity fire. Our results indicate susceptibility to the soil-borne pathogen Phytophthora cinnamomi is likely less problematic than previously postulated, yet more data and research is required before management is changed.