Community assembly relies on deterministic niche-based processes (e.g., biotic interactions), and stochastic sources of unpredictable variation (e.g., colonization history), that combined will influence late-stage community structure. When community founders present distinct functional traits and a colonization–competition trade-off is not operating, initial colonization can result in late-stage assemblages of variable diversity and composed by different species sets, depending if early colonizers facilitate or inhibit subsequent colonization and survival. By experimentally manipulating the functional identity of founders and predators access during the development of fouling communities, we tested how founder traits constrain colonization history, species interactions and thereby regulate community diversity. We used as founders functionally different fouling organisms (colonial and solitary ascidians, and arborescent and flat-encrusting bryozoans) to build experimental communities that were exposed or protected against predation using a caging approach. Ascidians and bryozoans are pioneer colonizers in benthic communities and also good competitors, but the soft-body of ascidians makes them more susceptible to predators than mineralized bryozoans. When ascidians were founders, their dominance (but not richness) was reduced by predation, resulting in no effects of predators on overall diversity. Conversely, when bryozoans were founders, both space limitation and predator effects resulted in species-poor communities, with reduced number and cover of ascidian species and high overall dominance at the end of the experiment. We, thus, highlight that current species interactions and colonization contingencies related to founder identity should not be viewed as isolated drivers of community organization, but rather as strongly interacting processes underlying species distribution patterns and diversity.

群落组装依赖于确定性的基于生态位的过程（例如，生物相互作用）和不可预测变异的随机来源（例如，殖民历史），这些结合将影响后期群落结构。当群落创建者表现出不同的功能特征并且殖民-竞争权衡没有发挥作用时，最初的殖民可能导致后期的可变多样性集合并由不同的物种集组成，这取决于早期殖民者是促进还是抑制随后的殖民和生存。通过在污染群落发展过程中实验性地操纵创始人和捕食者访问的功能身份，我们测试了创始人特征如何限制殖民历史、物种相互作用，从而调节群落多样性。我们使用功能不同的污垢生物（殖民地和孤立的海鞘，以及树状和扁平结壳的苔藓动物）作为创始人，以使用笼养方法建立暴露或防止捕食的实验群落。海鞘和苔藓动物是底栖群落的先驱殖民者，也是很好的竞争者，但海鞘的软体使它们比矿化苔藓动物更容易受到捕食者的攻击。当海鞘是创始者时，它们的优势（但不是丰富度）因捕食而减少，导致捕食者对整体多样性没有影响。相反，当苔藓动物是创始者时，空间限制和捕食者效应都会导致物种贫乏的群落，海鞘物种的数量和覆盖率减少，并且在实验结束时总体优势很高。我们，因此，