Effects of harvester ants on plant species distribution and abundance in a serpentine grassland |
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Authors: | Mark J F Brown Kathleen G Human |
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Institution: | (1) Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA e-mail: mark@ants.stanford.edu; fax: 415 723 6132 , US |
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Abstract: | Seed harvesting ants can have important effects on the composition and structure of plant communities. We investigated two
effects of Messor andrei, the black seed-harvesting ant, on a serpentine grassland plant community in northern California. First, to determine if
selective seed predation by ants affects plant community composition, we excluded harvester ants from 1-mediameter circular
plots of grassland. Abundances of all species on these plots and on control plots were measured before and after exclosure.
Second, to determine if M. andrei nest mounds affect plant community composition, we compared plant species abundances on and off nest mounds. M. andrei deposit large amounts of organic matter on their nest mounds over a foraging season, so mounds may alter the edaphic environment.
The exclusion of seed-harvesting activity did not cause changes in the plant community. Nest mounds had a strong effect on
plant communities: there were many more grasses and fewer forbs on ant mounds, although at least one forb, Lepidium nitidum, produced twice as many seeds when it grew on nest mounds. We found that nest mounds formed islands of higher-temperature
soil in the serpentine grassland.
Received: 31 March 1997 / Accepted: 6 May 1997 |
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Keywords: | Seed-harvesting ants Ant mounds Serpentine grassland Plant abundance Messor andrei |
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