Dispersal Kernels Dispersal Kernels are statistical models that represent the probability of seed dispersal from the source tree. Realistic biological data is required to complete the models, to accurately fill in variables such as: number of seeds, seed size, and reproductive age. Depending on the plant species, the variables in the equation will change. In the years since Reid hypothesized the methods for seed dispersal, the models have gained more complex elements which attempt to resolve Reid's Paradox. alt=|Dispersal Kernels representing seed frequencies at increasing distances from the parent tree|427x427px The dispersal of seeds from a parent tree are initially spread as a normal distribution, as predicted by a standard diffusion equation. However, biological phenomenon complicate the diffusion equation by adding biotic vectors of dispersal such as blue jays and eastern grey squirrels, species which possess caching behaviors, and abiotic agents of dispersal such as high velocity wind storms. These additional vectors of seed dispersal make the dispersal kernels have a "fat-tail", or a large kurtosis. This means that the probability of a long-range dispersal event is higher than that of the standard diffusion dispersal kernel. In order to resolve Reid's Paradox, the vector(s) of seed-dispersal, which give the dispersal kernel a fat-tail, must be identified. Possible Explanations for Reid's Paradox Animal Dispersal- Long distance seed-dispersal events due to animal-seed interactions (such as caching or endozoochorous dispersal) would fatten the tail of the dispersal kernels. To fully explain Reid's Paradox, these rare animal induced seed-dispersal events must have been more important during migration events than recognized or recorded currently. Cryptic Refugia- Small populations of plants may have grown closer to the ice sheets in microhabitats that possessed the habitat characteristics needed for growth and reproduction. This would minimize the actual post-glacial dispersal distance. Such hypothetical populations would not be abundant enough to leave fossil evidence, so have escaped detection. In North America, there is some genetic evidence of cryptic northern refugia for sugar maple and American beech.
Dispersal kernels Dispersal kernels are statistical models that represent the probability of seed dispersal from the source tree. Realistic biological data is required to complete the models, to accurately fill in variables such as: number of seeds, seed size, and reproductive age. Depending on the plant species, the variables in the equation will change. In the years since Reid hypothesized the methods for seed dispersal, the models have gained more complex elements which attempt to resolve Reid's Paradox. alt=|Dispersal Kernels representing seed frequencies at increasing distances from the parent tree|427x427px The dispersal of seeds from a parent tree are initially spread as a normal distribution, as predicted by a standard diffusion equation. However, biological phenomenon complicate the diffusion equation by adding biotic vectors of dispersal such as blue jays and eastern grey squirrels, species which possess caching behaviors, and abiotic agents of dispersal such as high velocity wind storms. These additional vectors of seed dispersal make the dispersal kernels have a "fat-tail", or a large kurtosis. This means that the probability of a long-range dispersal event is higher than that of the standard diffusion dispersal kernel. In order to resolve Reid's Paradox, the vector(s) of seed-dispersal, which give the dispersal kernel a fat-tail, must be identified. Possible explanations for Reid's Paradox Animal dispersal Long distance seed-dispersal events due to animal-seed interactions (such as caching or endozoochorous dispersal) would fatten the tail of the dispersal kernels. To fully explain Reid's Paradox, these rare animal induced seed-dispersal events must have been more important during migration events than recognized or recorded currently. Cryptic refugia Small populations of plants may have grown closer to the ice sheets in microhabitats that possessed the habitat characteristics needed for growth and reproduction. This would minimize the actual post-glacial dispersal distance. Such hypothetical populations would not be abundant enough to leave fossil evidence, so have escaped detection. In North America, there is some genetic evidence of cryptic northern refugia for sugar maple and American beech.
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Kernels Dispersal Kernels
kernels Dispersal kernels
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Explanations
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Cryptic Refugia-
Cryptic refugia