Parker Matthew A
Am Nat. 1999 May;153(S5):S48-S60. doi: 10.1086/303211.
Coevolution in mutualisms may result in a stable mosaic pattern of spatial differentiation, with regions occupied by different coadapted pairs of mutualists each being resistant to invasion by organisms with alternative phenotypes. The evolution of geographic mosaic patterns was analyzed for symbioses of legume plants and root-nodule bacteria (rhizobia), where plants are commonly polymorphic for genes affecting mutualism specificity. Typically, some alleles confer broad compatibility, and others restrict the set of bacterial genotypes accepted by plants as mutualist partners. Metapopulation simulation models with genetic assumptions matching the observed form of symbiotic specificity show that selection can generate a stable geographic mosaic if certain conditions are satisfied regarding competitive abilities, fitness benefits from mutualism, and migration rates. The structure of geographic variation in natural populations of the annual legume Amphicarpaea bracteata, together with patterns of variation in symbiotic fitness, is consistent with the interpretation that a mosaic pattern of differentiation may exist. Experimental and observational studies necessary to test more rigorously for mosaic distributions are outlined.
互利共生中的协同进化可能导致一种稳定的空间分化镶嵌模式，不同的互利共生适应对所占据的区域各自对具有替代表型的生物的入侵具有抗性。对豆科植物与根瘤菌（根瘤菌属）的共生关系的地理镶嵌模式的进化进行了分析，其中植物通常在影响共生特异性的基因上具有多态性。通常，一些等位基因具有广泛的兼容性，而其他等位基因则限制了植物作为共生伙伴所接受的细菌基因型的范围。具有与观察到的共生特异性形式相匹配的遗传假设的集合种群模拟模型表明，如果在竞争能力、互利共生的适应性益处和迁移率方面满足某些条件，选择可以产生稳定的地理镶嵌。一年生豆科植物两型豆自然种群的地理变异结构，以及共生适应性的变异模式，与可能存在分化镶嵌模式的解释一致。概述了更严格地检验镶嵌分布所需的实验和观察研究。
