Investigating the demographics and intrapopulation spatial patterns of the endangered Cycas megacarpa K.D.Hill in central Queensland, Australia

Abstract

Cycads are threatened globally due to land clearing and unsustainable harvesting impacting upon long-living mature plants that are essential for population viability. Cycas megacarpa K.D.Hill is an endangered cycad endemic to central Queensland, Australia. Populations of this species have been impacted by recent infrastructure projects resulting in translocation of individuals to ameliorate losses. Translocations require an understanding of the species demographics and intrapopulation spatial distributions to inform planting design. This project studied the demography and spatial patterns of a population of C. megacarpa (%5600 individuals) within a 96.3 ha area in central Queensland to design a translocation planting that replicates a healthy population. Descriptive statistics were used to analyse the demography of the population. Spatial Point Pattern Analyses (SPPA) were used to determine if the population's spatial arrangement departed from complete spatial randomness across height, gender classes and between female and juvenile cycads. We found this population to possess a 1:1 ratio of male and female cycads. However, male C. megacarpa were on average %0.5 m shorter than female cycads and reached reproductive maturity at shorter heights. SPPA found this population of C. megacarpa to be clustered irrespective of height or gender. A significant spatial relationship was detected between female and juvenile cycads. The results of this study suggest that to replicate a healthy C. megacarpa population, the translocated cycads could be planted in a clustered spatial pattern with known male and female individuals distributed through the clusters at a 1:1 ratio.