Global to local perspectives on seed dispersal

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Copyright: Thomson, Fiona
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Abstract
In this thesis, I explore how plant traits and landscape differences affect seed dispersal, a key life history stage in plants. It has long been assumed that dispersal capacity trades off with maternal provisioning, so that small-seeded species disperse further than do large-seeded species. My results, from a global, cross-species study, show that large-seeded species have greater mean and maximum dispersal distances than do small-seeded species. Surprisingly, maximum plant height had stronger explanatory power than did seed mass, and once height was accounted for there was only a slight trend towards small-seeded species having larger dispersal distances. Plant height has not previously been linked to species’ dispersal distances across and within dispersal syndromes. For most species, seed dispersal distances are not known; however dispersal syndromes can indicate short or long-distance dispersers. For the first time, I created a model which used basic plant and ecological traits to predict dispersal syndromes. Species’ dispersal syndromes were correctly predicted with greater than 50% accuracy for Australian, Californian and Swiss floras. This model can provide dispersal information for species where there has previously been none. Within species, larger seed size and reduced dispersal capacity have been linked to habitat isolation and fragmentation, but to date no cross-species comparisons of seed size and dispersal structure size have been made. I found no consistent pattern between the seed size or dispersal investment for species from fragmented compared to non-fragmented communities, indicating that species adapt differently to habitat fragmentation. Lastly, ant-seed dispersal systems in the Greater Blue Mountains World Heritage Area have not been previously studied, despite ~200 plant species relying on ant dispersal. A field study revealed differences in the dominant seed-dispersing ant genera between two elevations, with implications for seed removal rates and dispersal distances. This suggests that landscape scale change can significantly influence the dispersal ability of plant species. Overall, this thesis tests and reshapes our ideas of trade-offs between dispersal capacity and other plant traits. Additionally it establishes the importance of landscape changes and plant traits when looking at broad scale patterns in seed dispersal ranging from global to local scales.
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Author(s)
Thomson, Fiona
Supervisor(s)
Kingsford, Richard
Moles, Angela
Auld, Tony
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Publication Year
2012
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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