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 <i>Chlorella sorokiniana</i>: (1) the presence of the flagellate <i>Ochromonas danica</i> or the crustacean <i>Daphnia magna</i> leads to the formation of multicellular groups; (2) the formation of multicellular groups reduces predation by <i>O. danica</i>, but not by the larger predator <i>D. magna</i>; (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，是单细胞个体形成协作群体。故此，要理解多细胞性的起源与本质，我们需要厘清与多细胞群体形成相关的各项成本与收益。本研究以兼性多细胞藻类索氏小球藻（Chlorella sorokiniana）为实验材料，获得如下四项实验结果：（1）当环境中存在鞭毛虫达尼卡色金藻（Ochromonas danica）或甲壳类动物大型溞（Daphnia magna）时，会促使多细胞群体形成；（2）多细胞群体的形成可有效降低被达尼卡色金藻捕食的风险，但无法抵御体型更大的捕食者大型溞；（3）在光照强度较低、光照竞争更为激烈的培养条件下，多细胞群体的生长速度慢于单细胞个体；（4）在无活体捕食者的环境中，多细胞群体中的细胞占比会以不随光照强度变化的速率逐渐下降。上述研究结果可解释为何在索氏小球藻这类物种中，多细胞群体的形成是兼性的——即仅在捕食者存在时才会发生。