The diversity and distribution of microfungi in leaf litter of an Australian wet tropics rainforest

This thesis examines aspects of the diversity, distribution and taxonomy of microfungi in leaf litter of several tree species in an upland tropical rainforest of Far North Queensland, Australia.\ud \ud The first study assessed the advantages and limitations of the particle filtration method as a potential complementary approach for estimating microfungal diversity. The observed microfungal diversity was comparable to that reported for neotropical leaf litter fungi, with a total of 253 morphotypes observed among 1365 isolates from eight samples of Neolitsea dealbata leaf litter. The isolation rate was negatively correlated with the time that leaves had been stored in a dried state while the number of observed morphotypes was similar to the control after three weeks of storage. Surface treatment with sodium hypochlorite did not affect the isolation of internal colonisers while it reduced the number of propagules on the leaf surface. \ud \ud The diversity of microfungi could in part be explained by the dynamic nature of tropical leaf litter where decay processes advance rapidly. In a second study that examined decaying leaves of Ficus pleurocarpa, a total of 105 taxa were recorded using a direct observational method. Applying a particle filtration method, 53 taxa were detected among 562 isolates. Distinct differences in microfungal assemblages were observed at different stages of decay, which were characterised by a rapid replacement of microfungal species at early decay and increasing similarity of collections with advancing decay. \ud \ud Microfungal diversity was characterised in leaf litter of six tree species belonging to four plant families common to the region, namely the Elaeocarpaceae, the Lauraceae, the Moraceae and the Proteaceae using two isolation protocols. A total of 185 taxa were observed using the direct method and 419 morphotypes were recorded in the wet season and 276 morphotypes in the dry season using a particle filtration protocol. The observed diversity of microfungi differed between some tree species and also between isolation protocols. However, both isolation methods provided congruent results in terms of microfungal distributions. Microfungal leaf litter communities were strongly shaped by host phylogeny and seasonal factors. These results indicate that microfungi in tropical leaf litter are not random assemblages but rather communities with 'recognisable and measurable differences among repeating assemblages of fungi that occur simultaneously in similar habitats'. Species richness on leaves of different tree species was correlated with the level of total phenolics, leaf thickness and manganese. The role of chemical and physical leaf attributes in shaping overall distributional patterns as well as those of individual microfungal species requires further detailed studies. A high percentage of observed fungi were anamorphs and approximately 50 % of taxa could not be integrated into a phylogenetic scheme below the level of class. Nevertheless, families and orders previously reported from tropical habitats were also dominant among those fungi that could be integrated.\ud \ud While an assessment of interspecific interactions among fungi was beyond the scope of this study, interactions between a discomycete and a scolytine beetle were demonstrated and it was hypothesised that insect-fungi interactions may increase the efficiency of decomposition processes. \ud \ud For future studies of microfungal diversity, a centrifugal-phylogenetic approach may provide a useful strategy to extend the baseline information established in the present study. With this approach, closely related hosts are studied first and then more and more distantly related plants are included. Due to the high diversity of tree species at all taxonomic levels, the rainforests of the wet tropics of Australia would provide an ideal study site for ongoing research into the host recurrence of microfungal species