Dissertation Research: Experimental Evolution in Volvocine Algae

这个项目的目的是为了了解推动群居伏尔沃藻(Volvox及其近亲)细胞分化进化的选择压力。某些种类的海藻有两种细胞类型：专门用于繁殖的生殖细胞和专门用于运动的不育体细胞。物种间的趋势表明，这种分化可能是由于大群体繁殖成本的增加而演变的。为了验证这一假设，繁殖成本将在人工选择的大小不同的群体伏藻Pleodorina starrii中进行测量。不育体细胞的进化是多细胞生物体起源的关键一步，允许进一步分化为多种细胞类型和开发复杂的身体计划。不同功能细胞类型的发展所允许的复杂性的增加促进了植物和动物等大型多细胞生物的戏剧性辐射。Volvocine藻是多细胞进化的模式系统；了解这一组中细胞分化的起源可以阐明这种分化是如何在其他组中起源的。此外，由于体细胞牺牲自己的繁殖来造福于群体，了解体节的进化对于利他主义和合作的进化具有普遍意义。

The purpose of this project is to understand the selective pressures that drove the evolution of cellular differentiation in the colonial volvocine algae (Volvox and its close relatives). Some species of volvocine algae have two cell types: germ cells specialized for reproduction and sterile somatic cells specialized for motility. Trends among species suggest that this differentiation may have evolved in response to the increasing cost of reproduction in large colonies. To test this hypothesis, costs of reproduction will be measured in a colonial volvocine alga, Pleodorina starrii, artificially selected for large and small size. The evolution of sterile somatic cells was a critical step in the origin of multicellular organisms, allowing further differentiation into many cell types and the development of complex body plans. The increase in complexity allowed by the development of different functional cell types facilitated the dramatic radiations of large multicellular organisms such as plants and animals. The volvocine algae are a model system for the evolution of multicellularity; understanding the origins of cellular differentiation in this group can shed light on how such differentiation originated in other groups. Furthermore, because somatic cells sacrifice their own reproduction to benefit the colony, understanding the evolution of soma has implications for the evolution of altruism and cooperation in general.