OCE-PRF Track 1 (Broadening Participation): Evolutionary ecology of the "living solar panel" - how photosymbioses influence diversification of a marine bivalve lineage

在这项为期两年的博士后研究项目中，该研究员将使用双壳亚科Fragiae作为研究系统，研究光共生协会如何塑造海洋生物多样性。研究成果将有助于我们对生物多样性、宏观进化和海洋生态学的基础知识。该项目将在哈佛大学Colleen Cavanaugh博士的指导下进行。该项目包括多层次的外联活动，专门旨在扩大未被充分代表的群体对海洋科学的参与。无脊椎动物宿主和光合作用甲藻之间的光共生关系对珊瑚礁生态系统的营养和结构完整性至关重要。虽然人们已经致力于研究动物宿主和共生体之间的短期生态相互作用，但光共生对海洋后生动物长期进化动力学的影响却知之甚少。这在一定程度上是因为大多数海洋光共生群落是古老的(例如，珊瑚出现了200多年)。寄主目前的多样性和基因组被漫长而复杂的进化历史高度修改，这使得追踪由于光共生而产生的具体变化变得困难。双壳亚科是一个适合解决这一问题的系统，因为它包含一个独特的光共生谱系，最近(7MYA)从其非共生姐妹群中分离出来。这一组中的物种表现出对光共生生活方式的显著生态和形态适应。它们占据营养缺乏的栖息地，在那里不会出现非共生物种。一些物种拥有非常扁平的、类似太阳能电池板的外壳，以增加对共生体的阳光照射，或者具有微结构外壳特征，起到聚光透镜的作用。为了促进对这些光共生关系的理解，该研究员将在两个不同的水平上研究光共生对Fragiae的进化影响。在宏观进化水平上，将利用系统发育比较分析比较光共生和非光共生谱系之间的谱系多样性和贝壳形态进化模式。在基因组水平上，将对从印度-西太平洋和大西洋收集的12个Fragiae物种进行比较转录组分析。将确定参与光共生建立的候选基因，并探索它们在寄主的生理途径和壳形成中的功能。

In this two year postdoctoral research fellowship, the fellow will investigate how photosymbiotic associations shape marine biodiversification using the bivalve subfamily Fraginae as a study system. Research results will contribute to our fundamental knowledge of biodiversity, macroevolution and marine ecology. The project will be conducted under the mentorship of Dr. Colleen Cavanaugh at Harvard University. The project includes multi-level outreach activities that are specifically designed to broaden participation of underrepresented groups in ocean sciences.Photosymbiotic associations between invertebrate hosts and photosynthetic dinoflagellates are crucial to the trophic and structural integrity of coral reef ecosystems. Although extensive efforts have been devoted to study the short-term ecological interactions between animal hosts and their symbionts, the effects of photosymbiosis on long-term evolutionary dynamics of marine metazoans are less well understood. This is partially because most marine photosymbiotic associations are ancient (e.g., arising more than 200 MYA for corals). The hosts' present diversities and genomes are highly modified by long, complex evolutionary histories; this makes it difficult to trace specific changes due to photosymbioses. The bivalve subfamily Fraginae is an apt system to address this topic because it contains an exclusive photosymbiotic lineage that diverged recently (7 MYA) from its non-symbiotic sister groups. Species in this group exhibit remarkable ecological and morphological adaptations to the photosymbiotic lifestyle. They occupy nutrient-deficient habitats where non-symbiotic species do not occur. Some species possess greatly flattened, solar-panel-like shells to enhance sunlight exposure to the symbionts, or bear microstructural shell features which function as light condensing lenses. To advance understanding of these photosymbiotic associations, the fellow will investigate evolutionary impacts of photosymbioses on Fraginae at two distinct levels. At a macroevolutionary level, patterns of lineage diversification and shell morphological evolution will be compared between the photosymbiotic and non-photosymbiotic lineages using phylogenetic comparative analyses. At a genomic level, comparative transcriptome analyses will be performed on twelve Fraginae species collected from the Indo-west Pacific and Atlantic oceans. Candidate genes involved in the establishment of photosymbioses will be identified and their functions in the hosts' physiological pathways and shell formations will be explored.