Dataset for: The costs and benefits of multicellular group formation in algae

The first step in the evolution of complex multicellular organisms involves single cells forming a cooperative group. Consequently, to understand multicellularity, we need to understand the costs and benefits associated with multicellular group formation. We found that in the facultatively multicellular algae Chlorella sorokiniana: (1) the presence of the flagellate Ochromonas danica or the crustacean Daphnia magna leads to the formation of multicellular groups; (2) the formation of multicellular groups reduces predation by O. danica, but not by the larger predator D. magna; (3) under conditions of relatively low light intensity, where competition for light is greater, multicellular groups grow slower than single cells; (4) in the absence of live predators, the proportion of cells in multicellular groups decreases at a rate that does not vary with light intensity. These results can explain why, in cases such as this algae species, multicellular group formation is facultative, in response to the presence of predators.复杂多细胞生物演化的首要步骤，是单细胞类群形成协作性聚合群体。因此，要解析多细胞性的演化逻辑，我们需要明确多细胞群体形成所关联的适合度成本与收益。本研究以兼性多细胞藻类奇罗莱衣藻（Chlorella sorokiniana）为实验对象，得到如下四项研究结果：1. 当捕食者鞭毛虫丹宁金藻（Ochromonas danica）或甲壳类大型溞（Daphnia magna）存在时，该藻类会形成多细胞聚合群体；2. 多细胞群体的形成可降低被丹宁金藻捕食的概率，但无法抵御体型更大的捕食者大型溞；3. 在光照强度较低、光资源竞争更为激烈的环境下，多细胞群体的生长速率显著慢于单细胞个体；4. 在无活体捕食者的培养条件中，多细胞群体内的细胞占比会随培养时间下降，且该下降速率不受光照强度的影响。上述研究结果可解释，为何在该藻类这类物种中，多细胞群体的形成属于兼性策略——仅在捕食者存在的环境下才会触发该性状的表达。