The emerging invasive alien plants of the Drakensberg Alpine Centre, southern Africa

Abstract

An 'early detection'-based desktop study has identified 23 taxa as 'current' emerging invasive alien plants in the Drakensberg Alpine Centre (DAC) and suggests a further 27 taxa as probable emerging invaders in the future. These 50 species are predicted to become problematic invasive plants in the DAC because they possess the necessary invasive attributes and have access to potentially suitable habitat that could result in them becoming major invaders. Most of the 'current' emerging invasive alien plant species of the DAC are of a northern-temperate affinity and belong to the families Fabaceae and Rosaceae (four taxa each), followed by Boraginaceae and Onagraceae (two taxa each). In terms of functional type (growth form), most taxa are shrubs (9), followed by herbs (8), tall trees (5), and a single climber. The need to undertake a fieldwork component is highlighted and a list of potential study sites to sample disturbed habitats is provided. A global change driver such as increased temperature is predicted to not only result in extirpation of native alpine species, but to also possibly render the environment more susceptible to alien plant invasions due to enhanced competitive ability and pre-adapted traits. A list of emerging invasive alien plants is essential to bring about swift management interventions to reduce the threat of such biological invasions. InTRODuCTIOn

Alien plant species that invade high elevations are generalists: support for the directional ecological filtering hypothesis

“…; McDougall et al. ; Carbutt ). Under the ALH, alien species that have successfully colonized higher elevations would be expected to display traits related specifically to tolerance of the abiotic stresses experienced at these elevations (Pyšek et al.…”

“…In contrast, the Abiotic Limitation Hypothesis (ALH) proposes that increased environmental severity at higher elevations, due to e.g. lower temperatures, stronger winds and higher UV-B radiation, excludes species that lack adaptations to these severe conditions (Johnston & Pickering 2001;Becker et al 2005;Vil a et al 2007;McDougall et al 2011;Carbutt 2012). Under the ALH, alien species that have successfully colonized higher elevations would be expected to display traits related specifically to tolerance of the abiotic stresses experienced at these elevations (Py sek et al 2011).…”

Annual monitoring reveals rapid upward movement of exotic plants in a montane ecosystem

“…(Carbutt 2012;Wilson et al 2013). The impact of exotics on the biodiversity of this region is therefore likely to increase for some time to come.…”

Topographic Controls on Vegetation Changes in Alpine Tundra of the Changbai Mountains

“…Ropars and Boudreau (2012) discovered that shrub expansion was more intense on low altitude than on exposed hilltops at the forest-tundra ecotone of Quebec, Canada [39]. High alpine zones with harsh environmental conditions (e.g., cold temperatures, strong winds, poor soil nutrients) may be resistant to the encroachment by plant species with low environmental tolerances [38,40,41].…”