Game theory provides no explanation for seed size variation in grasslands |
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Authors: | Email author" target="_blank">Ove?ErikssonEmail author |
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Institution: | (1) Department of Botany, Stockholm University, 106 91 Stockholm, Sweden |
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Abstract: | Game theoretical models have been suggested to explain the maintenance of a remarkable variation in seed size across species
in most types of vegetation. According to these models, which are based on the existence of a trade-off between seed size
and seed number; smaller-seeded species can invade any species mixture due to their numerical advantage, and larger-seeded
species can invade any species mixture due to their competitive superiority over smaller-seeded species during recruitment.
However, till now, there is very limited evidence for seed size effects on recruitment interactions among different species.
An experiment was designed using 16 species in Swedish grasslands, varying 384-fold in seed size. Species were sown pairwise
and alone in disturbed versus undisturbed small plots in grazed versus ungrazed grassland, and the resulting recruitment was
recorded. Seedling densities in the experimental plots were within the natural range. Both disturbance and grazing had a positive
effect on recruitment. Seed size did not affect recruitment except from a tendency that increasing seed size made recruitment
less dependent on disturbance. Recruitment of smaller-seeded species was not affected by the presence of larger-seeded species.
Larger-seeded species did not generally win in direct contest. These results suggest that game theoretical models do not explain
maintenance of seed size variation across species in these grasslands. Alternative explanations for seed size variation are
that either small-scale heterogeneity provide conditions favouring a range of different seed sizes or other attributes than
seed size effectively determine recruitment. |
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Keywords: | Coexistence Plant life histories Seed size-seed number trade-off Seedling recruitment Semi-natural grasslands |
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