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University of KwaZulu-Natal (2019)

Fleshy-fruited invasive plant species in KwaZulu-Natal, South Africa : native avian seed dispersal and impact assessment

Bitani, Nasiphi.

Titre : Fleshy-fruited invasive plant species in KwaZulu-Natal, South Africa : native avian seed dispersal and impact assessment.

Auteur : Bitani, Nasiphi.

Université de soutenance : University of KwaZulu-Natal

Grade : Master of Science in the Discipline of Ecological Sciences 2019

Résumé partiel
Globally, alien plant species have been recognised as a major threat to biodiversity. The increased global trade and travel have resulted in the increased introduction of new species. Direct or indirect introductions of alien invasive plant species result in altered ecosystem functioning, negatively affect economies, human health and wellbeing. In forest systems, habitat fragmentation has major impacts on biodiversity including the facilitation of alien invasions. Habitat alteration creates disturbance zones that are associated with increased invasion success. South Africa, like other parts of the world, is severely affected by alien plant species. Fleshy-fruited invasive species are amongst the most damaging invasive species with major environmental, social and economic impacts. Fleshy-fruited invasive plant species integrate into local seed dispersal networks and form mutual relationships with local avian seed dispersers leading to increased invasion potential. The success of avian mediated seed dispersal is influenced by the functional traits of both the plant and avian seed dispersers. Considering the negative impacts of fleshy-fruited alien invasive species it is important to understand ecological processes leading to their successful spread and if high priority species are being targeted for management to guide policy and conservation. Understanding avian mediated dispersal is important as it gives insights into the species that could promote alien plant invasion. The aim of the present study was to assess avian seed dispersal, and ecological and socio-economic impacts of fleshy-fruited alien invasive plant species. The objectives were to (1) predict avian seed dispersers of fleshy-fruited alien invasive plant species ; (2) determine the assemblage of native avian species potentially dispersing the seeds of Lantana camara ; and (3) determine the socio-economic and ecological impacts of fleshy-fruited alien invasive plant species. Firstly, we predicted the avian seed dispersers of fleshy-fruited invasive plant species in the Indian Coastal Belt Forest of KwaZulu-Natal Province, South Africa using functional traits of avian species (body mass, gape width, bill length, degree of frugivory, foraging strategy, abundance and habitat specificity) and fleshy-fruited invasive plants (crop size, fruit size, seed size, number of seeds, plant height, plant habitat, fruiting period and derived invasiveness score). The results showed that small, abundant forest generalist avian species were potentially effective dispersers of fleshy-fruited invasive species. Fleshy-fruited invasive plant species that were more likely to persist in the disturbed Indian Coastal Belt Forest through avian-mediated seed dispersal were small-seeded, open habitat plants with relatively longer fruiting duration. Secondly, we assessed the role of native avian species in the potential dispersal of a highly invasive shrub Lantana camara of the family Verbenaceae in Pietermatzburg, KwaZulu-Natal, South Africa. Avian species visiting L. camara were observed and potential dispersal distances estimated.

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