Diversity and relationships of South Africa's fig-associated nematodes

Abstract

Parasitic nematodes of the fig microcosm have received limited attention in South Africa. I have assessed the molecular diversity of nematodes present in the native South African species and discovered 24 undescribed species. Two were previously described but the descriptions need reviewing. I have revised one of these descriptions in Chapter 3 and Chapter 4 is a description of a new species with unique features that may well be a new genus of nematode. How these nematodes interact with their hosts, fig and/or wasp, has not yet been fully established and I did a co-phylogenetic study to determine how these three organisms interact on an evolutionary scale. The plant parasitic nematodes Schistonchus and Ficophagus showed no coevolutionary patterns with the hosts. Parasitodiplogaster is necrophagous and relies on the wasp for its food sources but showed coevolutionary patterns with both fig and wasp. The latter pattern could be because the fig syconia can influence the nematode survival. To determine if presence of nematodes in a wasp influences the fitness of the wasp I did a biogeography study of the wasps and nematodes associated with Ficus burkei. The dataset obtained was not optimal, but I could generate haplotype networks for Parasitodiplogaster sycophilon, the pollinator wasp Elisabethiella stuckenbergi and the parasitic wasp Seres barbarus. The parasitic wasp showed the highest dispersal, which was expected, because nematodes do not generally pick these wasps as rides to the next generation of figs. The pollinator wasps were not observed in areas where F. burkei has only recently been cultivated and no specific patterns of dispersal were observed. As expected, the nematodes were only associated with figs that contained the pollinator wasp but did show some geographical isolation of haplotypes.