Insights into the invasion of the moth catcher vine, Araujia sericifera (Apocynaceae), in South Africa

Abstract

The moth catcher vine, Araujia sericifera Brotero (Apocynaceae), is a prevalent invader in many countries worldwide, where it has been reported to be a significant threat to biodiversity and agriculture. However, limited knowledge exists surrounding the ecology, invasion and impacts of A. sericifera in South Africa, challenging the implementation of management efforts. Therefore, this study sought to understand the vine's invasion within a South African context. To determine the density of A. sericifera in response to ecological and socio-economic predictors, its abundance along roads in 42 Johannesburg suburbs was measured. Additionally, A. sericifera abundance was recorded on foot within two nature reserves in Johannesburg, where density estimates were found to be 29 times higher than those obtained via roadside surveys. At a local scale, there was no evidence to indicate that vegetation, urban cover, and median household income influence A. sericifera density, suggesting that the vine establishes indiscriminately across Johannesburg. To determine whether this opportunistic behaviour was reflected in the vine's recruitment, its emergence rates in response to shaded and full-sun conditions were investigated. Seedling emergence was higher under shaded conditions (47.8%) than under full-sun (11%). Using MaxEnt models, environmental variables affecting the plant's distribution in South Africa were identified. Human disturbance had a permutation importance of 85.6%, indicating that A. sericifera's establishment is largely driven by disturbance. While A. sericifera appears to be in its lag phase of invasion and is unlikely to invade natural ecosystems in the short term, its abundance in the two nature reserves suggests that management should be prioritised during this lag phase, prior to its potential expansion into less-disturbed areas.