Lattice population dynamics for plants with dispersing seeds and Vegetative propagation |
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Authors: | Yuko Harada and Yoh Iwasa |
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Institution: | (1) Department of Biology, Faculty of Science, Kyushu University, 812 Fukuoka, Japan |
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Abstract: | The population dynamics of plants in a lattice structured habitat are studied theoretically. Plants are assumed to propagate
both by producing seeds that scatter over the population and by vegetative reproduction by extending runners, rhizomes, or
roots, to neighboring vacant sites. In addtion, the seed production rate may be dependent on the local density in the neighborhood,
indicating beneficial or harmful crowding effects. Two sets of population dynamical equation(s) are derived: one based onmean-field approximation and the other based onpair approximation (tracing both global and local densities simultaneously). We examine the accuracy of these approximate dynamics by comparing
them with direct computer simulation of the stochastic lattice model. Pair approximation is much more accurate than mean-field
approximation. Mean-field approximation overestimates the parameter range for persistence if crowding effects on seed production
are harmful or weakly beneficial, but underestimates it if crowding effects are highly beneficial. Dynamics may show bistability
(both population persistence and extinction) if the effect of crowding is strongly beneficial. If there is a linear trade-off
between seed production and vegetative reproduction, the equilibrium abundance of the population may be maximised by a mixture
of seed production and vegetative reproduction, rather than by pure seed production or by pure vegetative reproduction. This
result is correctly predicted by pair approximation but not by mean-field approximation. |
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Keywords: | vegetative reproduction seed production pair approximation local density crowding effect |
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