A major challenge in evolutionary biology has been to explain the variation in multicellularity across the many independently evolved multicellular lineages, from slime moulds to vertebrates. Social evolution theory has highlighted the key role of relatedness in determining multicellular complexity and obligateness; however, there is a need to extend this to a broader perspective incorporating the role of the environment. In this paper, we formally test Bonner's 1998 hypothesis that the environment is crucial in determining the course of multicellular evolution, with aggregative multicellularity evolving more frequently on land and clonal multicellularity more frequently in water. Using a combination of scaling theory and phylogenetic comparative analyses, we describe multicellular organizational complexity across 139 species spanning 14 independent transitions to multicellularity and investigate the role of the environment in determining multicellular group formation and in imposing constraints on multicellular evolution. Our results, showing that the physical environment has impacted the way in which multicellular groups form, highlight that environmental conditions might have affected the major evolutionary transition to obligate multicellularity.

中文翻译：

---

多细胞复杂性的进化：相关性和环境约束的作用

进化生物学的一个主要挑战是解释从粘菌到脊椎动物的许多独立进化的多细胞谱系中多细胞性的变化。社会进化理论强调了相关性在决定多细胞复杂性和义务性方面的关键作用；然而，有必要将其扩展到包含环境作用的更广泛的视角。在本文中，我们正式测试了 Bonner 1998 年的假设，即环境对于确定多细胞进化过程至关重要，聚集多细胞在陆地上进化得更频繁，而克隆多细胞在水中进化得更频繁。结合标度理论和系统发育比较分析，我们描述了跨越 14 个独立过渡到多细胞性的 139 个物种的多细胞组织复杂性，并研究了环境在确定多细胞群形成和对多细胞进化施加限制方面的作用。我们的研究结果表明，物理环境影响了多细胞群的形成方式，强调环境条件可能影响了主要的进化转变，以专性多细胞。