Dissertation Research: Experimental Evolution in Volvocine Algae

这个项目的目的是了解选择的压力，推动细胞分化的进化在群集藻（Volvox及其近亲）。一些种类的藻有两种细胞类型：生殖细胞专门用于生殖和不育的体细胞专门用于运动。物种之间的趋势表明，这种分化可能是为了应对大群体中繁殖成本的增加而进化的。为了验证这一假设，繁殖成本将在一种群集的藻中进行测量，这种藻被人为地选择为大小不同。不育体细胞的进化是多细胞生物起源的关键一步，允许进一步分化成许多细胞类型和复杂身体结构的发展。不同功能细胞类型的发展所允许的复杂性的增加促进了大型多细胞生物（如植物和动物）的戏剧性辐射。藻藻是多细胞生物进化的一个模式系统；了解这个群体的细胞分化的起源可以揭示这种分化是如何在其他群体中产生的。此外，由于体细胞牺牲自己的繁殖来造福群体，理解体细胞的进化对利他主义和合作的进化具有重要意义。

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.