The spacial dynamics of below-ground fungal communities : a study of pattern and process

Soil fungi are an important part of terrestrial ecosystems, having invaluable roles in decomposition, carbon storage and nutrient cycling processes. Despite this, their ubiquitous nature and the methodological challenges associated with studying their diversity, have led to the traditional belief that fungal communities show little spatial structure. However, with the rapid development of molecular methods, research is now indicating that below-ground fungal communities are spatially heterogeneous in response to environmental variables and that the spatial structure of such communities has important above-ground consequences, such as influencing plant community structure and plant productivity. Spatial patterns displayed by below-ground fungal communities are alone insufficient in order to gain an accurate insight into how the community dynamics contribute to ecosystem functioning. The importance of spatial and environmental factors is often strongly interrelated and their relative importance is generally context and scale dependent. The research presented in this thesis, therefore, combines the analysis of fungal community spatial patterns with models based on mechanisms that drive their assembly over a range of spatial scales and levels of community organisation. Patterns of soil fungal community assembly were sampled from separation distances of 20 cm to 500 km, over three experimental designs, and analysed by T-RFLP and high throughput sequencing. The roles of spatial distance, habitat type, edaphic characteristics, climatic conditions, vegetation type and the diversity of the plant 17 community, as well as phylogenetic relatedness, in shaping the observed fungal communities were considered by a range of multivariate and spatial statistics. Large scale fungal community patterns were found, spanning distances of between 100 and 500 km along the south-east coast of Australia, as well as at smaller scales of 20 cm to approximately 100 m, sampled in temperate and alpine/subalpine ecosystems. A distinct lack of spatial patterning existed for the sampled below-ground fungal communities at intermediate scales. Spatial distance was found to have an important role in shaping the detected community patterns, while environmental factors did not play a dominant role in shaping the fungal community, independently of other measured variables, at the scales at which spatial patterns were detected. The functional processes that shape community assembly were additionally considered by looking at the role of niche and neutral dynamics as well as by explicitly characterising the role of dispersal in shaping the metacommunity. Neutrality modeling suggested that niche-based assembly contributed to soil fungal community assembly at the investigated scales. However, the role of stochastic or deterministic assembly mechanisms in driving community structure depended on the strength of dispersal and the degree of niche overlap experienced by the community, ultimately supporting the continuum hypothesis of niche and neutral assembly. Moreover, differences in the characteristics of the metacommunity were shown to influence the processes by which local communities were structured, emphasising that ecological processes do not act at the same scale/s at which community patterns are evident. Overall, understanding both pattern and process of fungal community assembly is essential to contribute to predicting changes in fungal community structure and function, at spatially relevant scales. With this knowledge it will be possible to better 18 recognise the effects of environmental change on fungal communities, in order to manage and conserve the surrounding terrestrial environments accordingly

Reconstructing community assembly: the impacts of alternate histories on contemporary ecology

The complexity of ecological and evolutionary processes that govern species distributions has long presented a challenge to understanding community assembly history. The work presented here develops a conceptual framework for integrating phylogenetics and biogeography to reconstruct the assembly of communities, provides empirical support for the broad applicability of this framework, tests whether morphology can serve as a proxy for behavioral ecology, and develops a novel metric of assemblage vulnerability and shows how vulnerability is related to biogeographic history. This dissertation demonstrates the need to merge evolution and ecology to reconstruct community assembly, and provides a framework for doing so. Further, the findings presented here suggest that such an interdisciplinary approach has the potential to both reveal fundamental processes shaping the assembly of natural systems, and to illuminate the functions and properties of ecosystems based on the evolutionary histories of their constituent species