Population size, habitat and conservation status of an Endangered species, Macrozamia johnsonii (Zamiaceae)

摘要

Macrozamia johnsonii D. Jones & K. Hill is a locally endemic cycad (family Zamiaceae) with a restricted occurrence in north-eastern New South Wales and currently listed as Endangered. Based on recent field surveys, its mean population size is estimated as approximately 3.5 million mature plants, with the lower bound of the 95% confidence interval at 1.9 million mature plants. Thirty percent of the population occurs in a formal reserve. Macrozamia Johnsonii occurs in grassy eucalypt forest, shrubby wet sclerophyll forest and in rainforest. It occurs most frequently on steeply sloping sites with high moisture index. There are no immediate significant threats to the species although timber harvesting is judged to be a potential longer term threat to part of the population. The conservation status of Macrozamia johnsonii is assessed using IUCN criteria and thresholds, using population size and extent data from this study and a plausible range of values based on available circumstantial evidence for parameters for which quantitative estimates are not available. Based on this assessment, we regard the conservation status of Macrozamia,johnsonii to be in the category of Least Concern, and that its current listing as an Endangered species under the NSW Threatened Species Conservation Act (1995) needs to be revised.