Anther-smut fungal infection of South African Oxalis species: Spatial distribution patterns and impacts on host fecundity

The smut fungi (phylum Basidiomycota) contain various economically important virulent plant pathogens and may infect only specific plant organs such as flowers. Fungi may replace pollen of infected flowers with their own fungal spores, creating potential study systems for sexually transmitted diseases. An anther-smut fungus, Thecaphora capensis, was recently rediscovered infecting Oxalis flowers in the Greater Cape Floristic Region. This study aimed to provide insight into the ecology and spatial distribution patterns of T. capensis infection. Eight new Oxalis hosts were discovered over a wide geographic area. Two insect species were collected from infected flowers and both carried fungal spores, implicating them as fungal vectors. Host morphology and reproductive success of infected plants differed significantly to that of healthy Oxalis individuals. Nearest neighbour and Gabriel connectedness analyses revealed diseased plants to be spatially clumped, although this non-random distribution could be ascribed to clonality. We found no common tendency for diseased plants to be of a particular floral morph.