Graphical synopsis of the C·I·B approach, relating research foci to the stages of the invasion process 1
(Click to view larger image)
The C·I·B’s research targets all aspects of the phenomenon of biological invasions, all taxonomic groups and all ecosystems.
Better understanding of invasion patterns and processes is required, and options for management and remediation need to be explored (Fig. 1).
Each stage of the invasion process (pre-introduction; initial incursion; expansion; and dominance) demands its own tools, insights and types
of study. The C·I·B undertakes work in several overarching themes: Biological or biodiversity foundations; model systems; human
dimensions; basic inventories; modelling capacities; policy formulation and risk assessment. This suite of themes provides the scope for
cutting-edge work in invasion science, while providing opportunities to draw in students from diverse biological fields (from fundamental to
applied) and many other disciplines.
Among the most pressing problems facing biology currently are the identification of biodiversity responses to environmental change, how
such change may be mitigated by management interventions, and what adaptations humans might need to implement to maintain biodiversity. To
understand humanity’s options for managing these challenges, we need long-term observational data on ecological systems.
The C·I·B runs three long-term altitudinal transects, coupled with ongoing student projects and experimental work.
We study ant assemblages across an elevational gradient in the Cederberg (invertebrate data collection 2003 – 2013; climate monitoring is
ongoing) and across disturbed and undisturbed sites at schools and nearby protected areas as part of the
The Cederberg transect is mirrored by two others – one along Sani Pass and one in the Soutpansberg mountains. These transects are managed
with support from the C·I·B’s Northern Hub and core team members at the Universities of
In 2013 the C·I·B began working with the City of Cape Town
to develop protocols for the long-term monitoring of the status of invasive species in the city, and to assess the effectiveness of management
interventions. This work is ongoing and expanding.
Biodiversity foundations - Baseline data for pre-invasion states and comparisons
Recognizing the significance of the foundational aspects of biology and the social sciences within the context of invasion biology, and the
fact that human activities are not ontologically separate from other natural processes, the C·I·B has undertaken much
foundational work on biodiversity and social systems. This area continues to be highly productive and to interest students in fundamental
aspects of biodiversity science.
Model systems for understanding invasions and impacts and developing sustainable management strategies
Invasions are highly context dependent and this has bedevilled many attempts to arrive at generalizations that explain the success of
individual species or populations, predict the performance of new introductions, and craft robust and defendable management approaches. Model
systems are valuable for gaining insights into complex phenomena like biological invasions1. Four model taxonomic groups have been
identified to serve as focal areas for research at the C·I·B, and others are likely to be added to the list.
a. Australian acacias
About 70 species of Australian acacias have been introduced to South Africa, while 16 species are already invasive. Australian Acacias are
by far the most widespread invasive alien taxon in South Africa, have caused the most substantial impacts of any group, and are expensive to
manage. These plants have also led to many conflicts between stakeholders in a diversity of settings, preventing effective management of
b. Invasive birds
Despite being home to 48 non-native bird species, very little is known about the mechanisms, impacts and distributions of these taxa in
South Africa. C·I·B researchers work on several species of birds (e.g. rose-ringed parakeet, common starling and common myna).
Using invasive birds as a model system, ongoing and future works includes (i) formulating spread models heterogeneous landscapes with mixed
propagules, (ii) investigating the adaptive dynamics of dispersal in non-equilibrium range dynamics, specifically on the adaptation driven by
spatial sorting and source-sink dynamics, (iii) cross-region comparison (e.g., morphological trait adaption in common starlings in SA vs. in
Australia), (iv) mapping genetic and phylogeographic structure of non-equilibrium populations, and (v) quantifying the functional role of
invasive birds in local food webs and networks.
c. Ladybirds as a model group
Insects represent some of the worst invasive species worldwide and provide an excellent system to explore traits associated with invasiveness
and how this information can be used to prevent or reduce their impacts on native species and ecosystems. In contrast to plants, most insect
introductions are unintentional, thus minimizing bias in pre-introduction trait selection (except for bio-control species) and they have fast
generation times thereby providing the possibility to explore adaptation and competition with native species. Ladybirds have the added advantage
that evolutionary fitness consequences can be measured directly in experimental trials, they are easily maintained and can be exposed to a
variety of biotic and abiotic conditions with relatively little workspace required.
d. Xenopus laevis - A globally significant invasive amphibian
The African clawed frog, Xenopus laevis, is one of the world’s most widely distributed amphibians. Exported from the southwestern Cape for
pregnancy testing in the 1930s, it has since become a standard laboratory amphibian, and a model species in its own right. However, this success has
been commensurate with introductions into novel environments, both deliberate and accidental, such that the species is now invasive on four continents.
C·I·B researchers collaborate with colleagues from other countries that have invasive X. laevis populations to form a
multi-disciplinary team which will tackle autecology, demographics, physiology, performance, genetics and combine these into species distribution models.
e. Invasions in urban areas
Biological invasions cause many types of problems in urban areas, create special types of conflicts and require very different management
interventions to those applied in natural ecosystems. Invasive species are likely to be more prevalent in cities than in nearby natural areas
because of greater human activity, modified environmental conditions (e.g. gardens of alien plants provide obvious hotspots for the initiation
of invasions.), and high propagule pressure. Furthermore, attempts to manage them are often controversial because of the diversity of stakeholders
in an urban context. The C·I·B collaborates with the City of Cape Town to translate research findings into management action for
city-wide policies and programmes. Key research areas are the impacts of invasions on ecosystem services, prioritization of invasive species
management and restoration, novel ecosystems and conflicts of interests.
There is also a requirement under NEMBA for all organs of state (including municipalities) to provide invasive species management plans. There
is an urgent need to develop the science base upon which such plans can be developed, and much scope exists for linking such studies with ongoing
programmes in other parts of the world. The C·I·B will host an
international workshop on urban invasions in November 2016.
f. Agricultural pest insects as models for invasion
Agricultural pest insects constitute a major socio-economic challenge to sustainable agriculture and food security in Africa, especially
given their interaction with changing climates. Insect pests serve as excellent model systems for understanding terrestrial insect invasions.
C·I·B researchers are testing various theories of niche shift during invasion, experimental modification of physiological
performance or genetic interference techniques (e.g. RNAi), and developing novel control and intervention strategies (e.g. biocontrol) that do
not necessarily involve the application of chemical pesticides with potentially harmful residues or environmental contamination.
Detection, demonstration, responses and remediation
Once alien species have established and become invasive, their costs to biodiversity, ecosystem functioning and society are often very
high. Consequently, the detection of potentially invasive species, and the development of cost-effective strategies for documenting changes in
abundance and distribution are crucial requirements for reducing the rates, extent and impacts of biological invasions. The C·I·B
collaborates closely with the
Invasive Species Programme of SANBI2
to undertake scientific studies of invasive species that still have limited ranges and for which eradication is considered potentially
Demonstrating that invasive species have substantial biodiversity impacts is becoming increasingly important to justify the expensive
management interventions that are required and to counter misleading criticisms from various interest groups. Impacts of invasions are sometimes
obvious and dramatic, but often are more subtle but nonetheless influential. Detailed studies on impacts have only been done for a small
proportion of invasive species in South Africa3. Substantial further work remains to be done to understand the full spectrum of types
of impacts caused in different taxa in different ecosystems and to develop protocols for using impact assessments to inform prioritization and
Removal of invasive species and restoration efforts for native vegetation are effective in restoring system structure and functioning, but
determining which remediation options are most effective for restoring function is a complex task. There is much potential for using different
native taxa as indicators of impact and of recovery following remediation efforts. This research theme is of interest to conservation agencies
and NGOs in southern Africa, and priorities are defined in consultation with partner organisations.
Spekboom – widely planted for carbon capture
Global environmental change and ecosystem services
Climate change, habitat alteration, overexploitation and pollution all interact with biological invasions to alter the structure and
functioning of ecosystems and therefore the services they deliver. Much of the focus of invasion biology has been on impacts on ecosystem
function and on ways to reduce them. Increasingly, however, attention is being drawn to interactions among global change drivers and how these
may influence the invasion process and its consequences. The primary goal of this work is the delivery of information to improve South Africa’s
options for managing the effects of climate change, including adaptation and mitigation.
The human dimensions of biological invasions
The ornamental horticulture and pet trades provide particularly important challenges for management of invasions, and the C·I·B
conducts much research in these areas. There is an urgent need to explore the implications and consequences of invasive species management
programmes that have dual goals (e.g. invasive species control combined with job creation, upliftment, making furniture, turning biomass into
energy, turning stands of invasive trees into production forests or wood lots). The potential for defining and achieving trade-offs in such
cases needs to be explored. Unintended consequences of such practices (such as the creation of dependencies) are potentially huge problems for
the sustainability of such programmes.