Dissertation Research: Toxic algae as a model system for intransitive eco-evolutionary feedbacks promoting cooperation.

本项目将研究单细胞藻Prymnesium parvum的不同遗传菌株之间的相互作用如何控制有毒藻华的形成。当某些藻类物种变得高度丰富并向水中释放有害于野生动物或人类的毒素时，就会发生有毒藻类水华。虽然有毒水华的频率和严重程度一直在增加，但我们对导致这些物种变得高度丰富或死亡的因素的了解仍然非常有限。大多数研究都集中在环境因素，如水污染，如何影响水华的形成，但这种解释在许多情况下是不够的。在焦点物种的某些遗传菌株不产生毒素，这项研究将测试的独特的假设，在Prymnesium种群丰度的巨大变化，导致有毒和无毒的遗传菌株之间的合作和竞争。在自然界中，许多物种都表现出合作行为，即使这并不符合合作个体的最佳利益。这项工作的结果预计将对合作的演变产生重要的见解，并确定可用于控制有害藻华的管理战略。此外，该项目将涉及指导本科生和高中生，包括来自科学领域代表性不足的群体的个人。还计划举办公开讲座和每周一次的广播科学节目。形成有害水华的藻类物种产生的毒素往往具有化感作用，通过杀死异种藻类，减少种间竞争和向水中释放营养物质。通过这种方式，这些毒素似乎起到了“公益”的作用，使整个人口受益。在Prymnesium parvum中，最近分离出一种低毒性的“作弊者”菌株，其在单一培养和混合培养中的生长速率均显著高于有毒的“合作者”菌株。该系统提供了一个独特的机会，调查生态相互作用如何可能保持合作化感作用在非结构化的人口。如果低毒性菌株从毒性中获益，而不产生毒素，如何保持毒性？这个问题将通过实验室微观实验、菌株培养和显微镜观察相结合的方法来探讨。具体而言，相互入侵实验将被用来寻找TOX+，TOX-，和异源菌株之间的不传递性循环，以确定是否生态进化的反馈导致在这个藻类物种的毒性变化的维护。

This project will investigate how interactions among different genetic strains of the single-celled algae Prymnesium parvum control the formation of toxic algal blooms. Toxic algal blooms occur when certain algal species become highly abundant and release toxins into the water that harm wildlife or humans. Although toxic blooms have been increasing in frequency and severity, our understanding of the factors that cause such species to either become highly abundant or to die back is still very limited. Most research has focused on how environmental factors, such as water pollution, affect bloom formation, but this explanation is inadequate in many cases. In the focal species certain genetic strains do not produce toxins; this study will test the unique hypothesis that large changes in Prymnesium population abundance result from the cooperation and competition among toxic and non-toxic genetic strains. In nature, many species exhibit cooperative behavior, even when it is not in the best interest of the cooperating individuals. Results from this work are expected to yield important insights into the evolution of cooperation and identify management strategies that can be used to control harmful algal blooms. In addition, the project will involve mentoring both undergraduate and high school students, including individuals from groups that are underrepresented in the sciences. Public lectures and a weekly radio science show are also planned.Algal species that form harmful blooms produce toxins that often function allelopathically, by killing heterospecifics, decreasing interspecific competition and releasing nutrients into the water. In this way, these toxins appear to function as a 'public good' by benefiting the entire population. In Prymnesium parvum, a low-toxic 'cheater' strain has recently been isolated that has a significantly higher growth rate than toxic 'cooperator' strains both in monoculture and in mixed culture. This system offers a unique opportunity to investigate how ecological interactions may maintain cooperative allelopathy in unstructured populations. How can toxicity be maintained, if low-toxicity strains reap the benefits of toxicity while not contributing to toxin production? This question will be explored using a combination of laboratory microcosm experiments, strain culturing, and microscope observation. Specifically, mutual invasibility experiments will be used to look for intransitivity cycles between TOX+, TOX-, and a heterospecific strain in order to determine whether eco-evolutionary feedbacks lead to maintenance of toxic variation in this algal species.