Fungi associated with Aizoaceae seed in the Succulent Karoo

Abstract

The Aizoaceae, commonly known as mesembs or “ice plants”, is a plant family endemic to Namaqualand, an area inside the Succulent Karoo biodiversity hotspot in South Africa. The more than 1800 unique mesembs are in part characterised by their hygrochastic seed capsules dispersing their seed by jet action. Six capsule types: Mesembryanthemum-, Delosperma-, Drosanthemum-, Lampranthus-, Ruschia- and Leipoldtia-type are distinguished by differences in funicles, covering membranes and closing bodies. With the existence of microbial endemism, now widely recognised, research into community ecology in the Succulent Karoo is needed to enable proper conservation. Sadly the microbial life associated with Aizoaceae has received little attention, Alternaria, Colletotrichum and Fusarium, have however been isolated from the halophyte Sesuvium portulacastrum, one of the few species from Aizoaceae but not endemic to South Africa. Fungi are known to aid in germination, seedling establishment, growth, water relations and nutrition in the Cactaceae (a family closely related to Aizoaceae). We believe that fungi may play a role in the ability of Aizoaceae to thrive in Namaqualand due to their specialization in the form of thick-walled spores that remain viable and have the ability to grow slow even at extreme aridity. We have isolated species of Alternaria, Aspergillus, Bipolaris, Cladosporium, Fusarium and Talaromyces from seeds of common mesemb species from Namaqualand. This is the first report of fungi associating with the specialised propagative material of Aizoaceae.