The evolutionary transition to multicellularity has occurred on numerous occasions, but transitions to complex life forms are rare. Here, using experimental bacterial populations as proxies for nascent multicellular organisms, we manipulate ecological factors shaping the evolution of groups. Groups were propagated under regimes requiring reproduction via a life cycle replete with developmental and dispersal (propagule) phases, but in one treatment lineages never mixed, whereas in a second treatment, cells from different lineages experienced intense competition during the dispersal phase. The latter treatment favoured traits promoting cell growth at the expense of traits underlying group fitness – a finding that is supported by results from a mathematical model. Our results show that the transition to multicellularity benefits from ecological conditions that maintain discreteness not just of the group (soma) phase, but also of the dispersal (germline) phase.

中文翻译：

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元人口结构和向多细胞性的进化过渡。

向多细胞性的进化过渡已经发生过很多次，但是向复杂生命形式的过渡却很少。在这里，我们使用实验细菌种群作为新生多细胞生物的代理，我们操纵影响群体进化的生态因素。各组在需要通过生命周期繁殖的制度下繁殖，该生命周期充满了发育和分散（繁殖）阶段，但是在一种处理谱系中从未混合，而在第二种处理中，来自不同谱系的细胞在分散相期间经历了激烈的竞争。后者的治疗偏爱于促进细胞生长的性状，而牺牲了适合群体的性状-这一发现得到了数学模型结果的支持。