Ant dispersal and predation affects the availability of seeds for old-field recolonisation in Western Australia
Harris, R.J. and Standish, R.J. (2008) Ant dispersal and predation affects the availability of seeds for old-field recolonisation in Western Australia. Journal of the Royal Society of Western Australia, 91 (4). pp. 301-311.
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Seed arrival onto abandoned farmlands (old-fields) in south-western Australia can be limited by their proximity to native remnant vegetation. As the major seed-harvesting guild, ants could affectseed availability on old-fields by either: (1) affecting the dispersal of elaiosome-bearing seeds from adjacent remnants; (2) thieving the elaiosome from seeds without affecting their dispersal onto old-fields; or (3) predating seeds, which reduces the availability of seeds for dispersal. The relative importance of these ant-seed interactions will depend on the rates of ant-mediated seed dispersal from the remnants onto the old-field, as well as the rates of seed predation across these habitats. We sampled the ant communities within two old-fields, within the adjacent eucalypt woodland remnants and at the boundaries of these two habitats, using pitfall traps to determine the relative proportions of seed dispersers, elaiosome thieves and seed harvesters within each zone–ants were assigned to these groups on the basis of our observations of ant-seed interactions. During these observations, we followed the fate of elaiosome-bearing Acacia seeds that were offered to antswithin each zone, primarily to estimate rates of seed dispersal and elaiosome thieving. We also offered eucalypt seeds to ants in feeding stations to estimate seed predation within each zone. We found that the relative proportions of seed dispersers, elaiosome thieves and seed harvesters were similar across zones, despite differences in the species composition between sites and a reduction in species richness in the old-fields. None of the Acacia seeds that we offered were dispersed from either remnant into the adjacent old-field. The majority of dispersal events were less than 3.6 mfrom the seed source (61%; n = 74) and dispersal beyond 20 m was rare (4%; maximum 28.1 m). Rates of elaiosome thieving and seed predation were not elevated in the old-fields compared with their rates in the other zones. Overall, the data indicate that ant-mediated seed dispersal onto old-fields was rare and seed predation by ants was similar across habitats.
|Publication Type:||Journal Article|
|Publisher:||Royal Society of Western Australia|
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