Developments and prospects for biological control of Prosopis (Leguminosae) in South Africa

South Africa was the first country to deploy biological control (biocontrol) against invasive Prosopis populations. Developments in this regard have been ongoing, and have been reviewed, at approximately 10-year intervals, since 1991. This review spans the period 2011-2020, a timespan globally characterised by increased awareness of the impacts of invasive Prosopis populations, and recognition of the need for improved management. Concerted international collaboration has resulted in enhanced clarity on phylogenetic relationships within the Leguminosae and the phylogenetic placement of Prosopis. These advances have improved the framework for interpreting the host range of potential agents and for evaluating risk. At the outset of the biocontrol programme, in the 1980s, only agents that consumed mature seeds were considered. The intention was to reduce the invasiveness of Prosopis while simultaneously retaining it as a usable resource. The programme was subsequently expanded to investigate agents that prevent pod set or maturation of seed. More recently, potential agents that damage the vegetative growth of the plants have been included in response to recognition in South Africa, that there is no other route to successful management of Prosopis. There is a wealth of largely unexplored potential in this regard

Developments and prospects for biological control of Prosopis (Leguminosae) in South Africa

South Africa was the first country to deploy biological control (biocontrol) against invasive Prosopis populations. Developments in this regard have been ongoing, and have been reviewed, at approximately 10-year intervals, since 1991. This review spans the period 2011-2020, a timespan globally characterised by increased awareness of the impacts of invasive Prosopis populations, and recognition of the need for improved management. Concerted international collaboration has resulted in enhanced clarity on phylogenetic relationships within the Leguminosae and the phylogenetic placement of Prosopis. These advances have improved the framework for interpreting the host range of potential agents and for evaluating risk. At the outset of the biocontrol programme, in the 1980s, only agents that consumed mature seeds were considered. The intention was to reduce the invasiveness of Prosopis while simultaneously retaining it as a usable resource. The programme was subsequently expanded to investigate agents that prevent pod set or maturation of seed. More recently, potential agents that damage the vegetative growth of the plants have been included in response to recognition in South Africa, that there is no other route to successful management of Prosopis. There is a wealth of largely unexplored potential in this regard

Unresolved native range taxonomy complicates inferences in invasion ecology : Acacia dealbata Link as an example

CITATION: Hirsch, H. et al. 2017. Unresolved native range taxonomy complicates inferences in invasion ecology : acacia dealbata Link as an example. Biological Invasions, 19(6):1715-1722. doi:10.1007/s10530-017-1381-9The original publication is available at https://www.springer.com/journal/10530Elaborate and expensive endeavours are underway worldwide to understand and manage biological invasions. However, the success of such efforts can be jeopardised due to taxonomic uncertainty. We highlight how unresolved native range taxonomy can complicate inferences in invasion ecology using the invasive tree Acacia dealbata in South Africa as an example. Acacia dealbata is thought to comprise two subspecies based on morphological characteristics and environmental requirements within its native range in Australia: ssp. dealbata and spp. subalpina. Biological control is the most promising option for managing invasive A. dealbata populations in South Africa, but it remains unknown which genetic/taxonomic entities are present in the country. Resolving this question is crucial for selecting appropriate biological control agents and for identifying areas with the highest invasion risk. We used species distribution models (SDMs) and phylogeographic approaches to address this issue. The ability of subspecies-specific and overall species SDMs to predict occurrences in South Africa was also explored. Furthermore, as non-overlapping bioclimatic niches between the two taxonomic entities may translate into evolutionary distinctiveness, we also tested genetic distances between the entities using DNA sequencing data and network analysis. Both approaches were unable to differentiate the two putative subspecies of A. dealbata. However, the SDM approach revealed a potential niche shift in the non-native range, and DNA sequencing results suggested repeated introductions of different native provenances into South Africa. Our findings provide important information for ongoing biological control attempts and highlight the importance of resolving taxonomic uncertainties in invasion ecology.Publisher’s versio