Geritz S A, van der Meijden E, Metz J A
Department of Zoology, University of Maryland, College Park, Maryland 20742, USA.
Theor Popul Biol. 1999 Jun;55(3):324-43. doi: 10.1006/tpbi.1998.1409.
We present a model for the evolutionary dynamics of seed size when there is a trade-off between seed size and seed number, and seedlings from large seeds are better competitors and have a higher precompetitive survival than seedlings from small seeds. We find that strong competitive asymmetry, high resource levels, and intermediate harshness of the precompetitive environment favor coexistence of plants with different seed sizes. If the evolution of seed size is mutation-limited and single mutations have only a small phenotypic effect, then an initially monomorphic population reaches the final evolutionarily stable polymorphic state through one or more discrete evolutionary branching events. At each such branching event, a given lineage already present in the population divides into two phenotypically diverging daughter lines, each with its own seed size. If the precompetitive survival of seeds and seedlings is high for small and large seeds alike, however, evolutionary branching may be followed by the extinction of one or more lineages. Various results presented here are model-independent and point the way to a more general evolutionary bifurcation theory describing how the number and stability properties of evolutionary equilibria may change as a consequence of changes in model parameters.
我们提出了一个种子大小进化动力学模型，该模型考虑了种子大小与种子数量之间的权衡，并且大种子的幼苗比小种子的幼苗更具竞争力，且在竞争前具有更高的存活率。我们发现，强烈的竞争不对称性、高资源水平以及竞争前环境的中等严酷程度有利于不同种子大小的植物共存。如果种子大小的进化受突变限制，且单个突变仅产生较小的表型效应，则最初的单态种群会通过一个或多个离散的进化分支事件达到最终的进化稳定多态状态。在每个这样的分支事件中，种群中已有的一个特定谱系会分裂为两个表型不同的子谱系，每个子谱系都有其自身的种子大小。然而，如果小种子和大种子在竞争前的存活率都很高，那么进化分支之后可能会有一个或多个谱系灭绝。这里给出的各种结果与模型无关，并为更一般的进化分支理论指明了方向，该理论描述了进化平衡点的数量和稳定性如何因模型参数的变化而改变。
