Abstract:
The biodiversity in the Cape Floristic Region of South Africa faces many threats
from anthropogenic sources such as the trade associated with our globalized economy.
Aggressive plant pathogens in the genus Phytophthora are of particular concern because
of their capacity to invade and change plant communities and their frequent
dissemination via global trade. The fact that South Africa has a developing economy with
many socioeconomic challenges, the capacity to monitor the abundance of plants
imported for pests and pathogens is largely inadequate. Consequently, low cost methods
to enhance post-border surveillance for the emergence of Phytophthora species are
critically needed in South Africa. Therefore, the major aims of the research conducted in
this thesis were to: 1) reveal the diversity and potential threats of Phytophthora species
already present within the Cape Floristic Region, and 2) provide information and an
example of an approach to enhance the biosecurity with public engagement in South
Africa. Through independent sampling and a newly developed citizen science program,
this body of work revealed the presence of seventeen described Phytophthora species,
one informally described Phytophthora species, and three putative hybrids. Seven of
these Phytophthora species were not previously known to occur in South Africa. The
work also revealed a relationship between the invasion of P. cinnamomi and the health of
trees and evidence is provided for dissimilarity between invaded and non-invaded plant
communities. In addition, through a synthesis of modern Phytophthora species
descriptions and a diversity study in botanical gardens, it was possible to provide
evidence for the importance of surveying urban environments. Then as a means to
demonstrate the potential of public engagement to enhance biosecurity, the findings from
activities in Cape Citizen Science have been summarized. In this case it was possible to
show that nine of the Phytophthora species were recovered only because of citizen
participation. Cumulatively, this thesis has advanced the base of knowledge regarding the
presence and consequences of Phytophthora species in the Cape Floristic Region. In this
sense, they also provide valuable information and a model system to enhance biosecurity
in South Africa as well as in countries with similar economies.
