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Explora: Environment
and Resource Data should determine biocontrol success

observed due to a possible latency to the observed change At present, only one investigation was made during
in the area occupied. This view is based on most of the the same season on most of the seed bank dynamic stages
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released agents being seed-reducing agents which do not of three of the worst invasive Australian Acacia spp. in
directly influence plant occupancy. Rather, the agents South Africa (i.e., Acacia longifolia, A. pycnantha, and
have an indirect effect through influencing the rate of A. saligna). 13-15 This investigation was done many years
recruitment into existing and new populations. Therefore, after the biocontrol programs on these invasive Acacia spp.
studies on the plant’s seed bank dynamics are required were declared successful. 8-10,12 Studies by Strydom et al.
to assess whether any changes in the long term can be (covering all aspects of these species’ reproductive cycle)
expected (Figure 1). clearly demonstrated that the seed-reducing biocontrol

In general, the seed bank dynamics of these plants agents have not been effective in curbing pod and seed
are poorly understood. 27,41 For many of the invasive production to the extent that changes in the seed banks
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Australian Acacia spp. on which seed-reducing biocontrol can be observed. For A. saligna, the only species for
has been instigated, there is a lack of data for all stages of which pre-biocontrol release seed bank data are available
their seed bank dynamics (e.g., Acacia baileyana, Acacia for statistical testing, no change in the plant’s seed banks
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podalyriifolia, Acacia pycnantha) (Table 2). Furthermore, was found between pre- and post-biocontrol releases.
for many of the species for which data have been collected, Furthermore, there are also no data to suggest that the
not all stages of the seed bank dynamic process have been seed banks of the other Australian Acacia spp. will behave
investigated, data on the various stages have been collected differently pre- and post-biocontrol release (Table 2).
in isolation, or data on the stages before the release of the It has been assumed that current seed banks of invasive
agents were not collected (Table 2). Australian Acacia spp. in South Africa are the legacy of

Figure 1. Simplistic model illustrates the seed bank dynamics of any sexually reproducing plant (adapted from Simpson et al. ). At each phase in the
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process, namely seed production (1), primary dispersal (2), the seed bank (3), and seed germination (4), every individual seed has to overcome mortality
factors (e.g., predation, decay, etc.). At each phase, a proportion of the seed population will be lost and the surviving individuals will continue to overcome
the next set of obstacles. Comprehensive studies of processes linked to seed banks can measure the effectiveness of seed-reducing biological control agents.

Volume 2 Issue 1 (2025) 5 doi: 10.36922/eer.5876