Impact of poaching on the population structure and insect associates of the Endangered Encephalartos eugene-maraisii from South Africa

Abstract

Background: South Africa is an important centre of cycad diversity in Africa, however, the country’s cycads face extinction. Among the primary causes is the poaching of plants from the wild, even within protected areas. Objectives: This study examined poaching patterns in a local population of the Endangered Encephalartos eugene-maraisii I.Verd. and how it might affect the population structure, sex ratios, as well as interactions with associated insects. Methods: The population was surveyed in 2008 and 40% of this population was resurveyed between 2021 and 2022. We mapped missing cycads and generated heatmaps. Lastly, we investigated whether the proportion of stems from different size classes, sex ratios and abundance of insect associates varied between areas with a high and low poaching incidence. Results: Poaching, defined as the illegal removal of individuals from the wild, occurred 1.5 times more frequently along the border fence line than areas further away. Medium-sized stems (21–80 cm) are primarily targeted (likely as they can be carried more easily) and low proportions of these stems remain in areas with a high poaching incidence. While E. eugene-maraisii exhibits some resilience against poaching through basal suckering, it takes several decades for suckers to mature and replace harvested stems. No effect on sex ratios were recorded in areas with a high poaching incidence, suggesting poachers have not deliberately selected female or male cycads at this site. No pollinating insects were detected on E. eugene-maraisii, and no seedlings were observed. Conclusion: Cone production may be too rare in diminished populations to support pollinators that utilise cones as brood sites. The presence of insects that use other plant parts, including leaves, dried leaf stalks and cycad trunks, in the larger population suggests that they are more resilient to diminishing host populations. However, these insects were absent in smaller populations, and their abundances were lower in low-density sites and smaller clump sizes of their host in the larger population. This suggests these insects may be vulnerable to the decline of their host populations due to poaching.