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UBC Theses and Dissertations

Community structure of arbuscular mycorrhizal fungi along an altitudinal gradient Egan, Cameron Patrick


A fundamental goal in ecology is to examine diversity patterns of naturally occurring communities and link these patterns to underlying structuring processes. Despite the importance of arbuscular mycorrhizal (AM) fungi in natural ecosystems, the majority of studies to date have focused on community structure in a restricted set of systems (mainly temperate grasslands, old fields, and agricultural ecosystems). This is highly limiting because it is well known that the functioning of mycorrhizal symbioses can be influenced by biotic and abiotic environmental factors, and thus our understanding of how mycorrhizas are structured and function across a wide variety of habitats is limited. Furthermore, with recent advances in next generation sequencing (NGS) technology, it is timely to begin a more thorough investigation of AM fungi across a wide variety of habitat types. The objectives of this thesis were to determine whether (1) modern NGS techniques accurately depict AM fungal communities using mock communities, (2) environmental filtering along an elevation gradient influences the phylogenetic structure of AM fungal communities in the soil, (3) habitat filtering or plant host selection is a stronger determinant of AM fungal communities along an elevation gradient, and (4) aerial dispersal of AM fungal spores varies among a wider variety of North American habitat types. Examination of sequences generated from mock AM fungal communities revealed that taxonomic assignment of sequences within AM fungal families closely matched expected abundances, but accuracy decreased at lower taxonomic levels. However, analyses revealed that semi-quantitative metrics of sequence data still accurately inform on ecological patterns. Along elevation gradients AM fungal communities were observed to be more phylogenetically related than is expected by chance within all elevations sampled. In addition, AM fungal communities sampled from three co-occurring plant hosts revealed that communities are more strongly influenced by elevation sampled than host identity. Aerial dispersal also appears to be influenced by habitat type, where the highest proportion AM fungal spores in the air relative to in the soil was highest in more arid systems. Collectively, these studies indicate that local environmental conditions strongly influence assembly processes of AM fungal communities.

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