Rainey Paul B, Rainey Katrina
Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
Nature. 2003 Sep 4;425(6953):72-4. doi: 10.1038/nature01906.
A fundamental problem in biology is the evolutionary transition from single cells to multicellular life forms. During this transition the unit of selection shifts from individual cells to groups of cooperating cells. Although there is much theory, there are few empirical studies. Here we describe an evolutionary transition that occurs in experimental populations of Pseudomonas fluorescens propagated in a spatially heterogeneous environment. Cooperating groups are formed by over-production of an adhesive polymer, which causes the interests of individuals to align with those of the group. The costs and benefits of cooperation, plus evolutionary susceptibility to defecting genotypes, were analysed to determine conformation to theory. Cooperation was costly to individuals, but beneficial to the group. Defecting genotypes evolved in populations founded by the cooperating type and were fitter in the presence of this type than in its absence. In the short term, defectors sabotaged the viability of the group; but these findings nevertheless show that transitions to higher orders of complexity are readily achievable, provide insights into the selective conditions, and facilitate experimental analysis of the evolution of individuality.
生物学中的一个基本问题是从单细胞到多细胞生命形式的进化转变。在这个转变过程中，选择的单位从单个细胞转移到了合作细胞群体。虽然有很多理论，但实证研究却很少。在这里，我们描述了在空间异质环境中繁殖的荧光假单胞菌实验群体中发生的一种进化转变。合作群体是通过过度产生一种粘性聚合物形成的，这使得个体的利益与群体的利益保持一致。分析了合作的成本和收益，以及对背叛基因型的进化敏感性，以确定是否符合理论。合作对个体来说成本高昂，但对群体有益。背叛基因型在由合作类型建立的群体中进化，并且在有这种类型存在时比没有时更具适应性。短期内，背叛者破坏了群体的生存能力；但这些发现仍然表明，向更高层次复杂性的转变很容易实现，为选择条件提供了见解，并促进了对个体进化的实验分析。
