Seed dispersal mutualisms are important ecological interactions that can shape plant communities by influencing species distributions, community composition, and the regeneration of populations following a disturbance. Considering the fundamental role seed dispersal mutualisms play in many plant communities, it is important to understand, both generally and for individual seed dispersal mutualisms, what determines when animal partners successfully disperse seeds and when they do not. Myrmecochory, the dispersal of seeds by ants, is the most common form of zoochory in Western Australia. Myrmecochore plant diversity is richest in the Kwongan sandplains of the south-west, where ant-dispersed species can make up as much as 36% of the plant community. Here, I studied the determinants of seed dispersal rates to understand local variation in myrmecochorous seed dispersal rates. At a series of 30 sites, we sampled the ant and plant communities, measured aspects of the community structure (vegetation height, openness, topography, soil), measured seed removal rates and observed ant-seed interactions. The most significant factor that governed seed removal rates was the presence of the ant species Rhytidoponera violacea. Additionally, during seed dispersal observation trials, R. violacea removed 95% of all seeds taken. To better understand the fate of Acacia blakelyi seeds dispersed by R. violacea, we simulated variable seed burial depths and elaiosome removal by ants, followed by a bushfire to stimulate germination. Seed burial depth had a significant effect on seedling emergence, with the proportion of emerged seedlings declining with burial depth. The effect of depth was due to the strength of a fire-cue (heat) declining with depth. Seed burial depth also had a fitness cost, with a greater proportion of ârobustâ seedlings emerging from seeds buried closer to the surface. Seeds buried too deep to receive fire-cues remained dormant, adding to a long-lived soil seed bank.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-12112008-142107 |
| Date | 23 December 2008 |
| Creators | McCoy, Neil L |
| Contributors | Nick M Haddad, William A Hoffmann, Rob R Dunn |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-12112008-142107/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dis sertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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