Post-dispersal predation on Pinus sylvestris seeds by Fringilla spp: ground substrate affects selection for seed color |
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Authors: | O Nystrand Anders Granström |
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Institution: | Swedish University of Agricultural Sciences, Department of Forest Vegetation Ecology, S-901 03 Ume?, Sweden fax: +46-90-16 66 12; e-mail: Ove.Nystrand@svek.slu.se, SE
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Abstract: | Background matching might lower the risk of seeds being eaten by seed predators that search visually. In aviary experiments,
we analyzed the selection of diff erent-colored seeds by ground-feeding finches (Fringillacoelebs and F.montifringilla) against four naturally occurring forest soil substrates. The substrates were fresh burn (black), 6-year-old burn (brown),
mineral soil (pale yellow) and Pleuroziumschreberi feather moss (green). We used color-sorted seeds of Pinussylvestris, a species with a large natural variation in seed color, ranging from pale yellow to black. Although seeds were scattered
on the substrates at a density of only 91 seeds m−2, birds removed seeds effectively. Both bird species found more pale than dark seeds on the fresh burn substrate. F. montifringilla also recovered more pale than dark seeds on the old burn, and more dark than pale seeds on mineral soil. In moss, the birds
found very few seeds compared to the other substrates, and there was no color discrimination. P.sylvestris is frequently regenerating after fire, suggesting that dark seeds would be favored under selection from visually searching
predators. Fire-adapted conifers with serotinous cones, e.g., Pinuscontorta ssp. latifolia, which spread their seeds primarily on freshly burnt surfaces, produce uniformly black or dark brown seeds. However, regeneration
of the non-serotinous P.sylvestris is often extended for several years after a fire, during which substrate color and structure change. This may have helped
to maintain variation in seed color. When regeneration of a plant species occurs on a substrate of uniform color, we believe
that selection by visually searching seed predators will result in the evolution of cryptic seed color.
Received: 16 August 1996 / Accepted: 30 November 1996 |
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Keywords: | Post-dispersal seed predation Seed color Crypsis Evolution Regeneration |
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