The Evolution and Diversification of a Symbiotic Bioluminescence Signaling System

美国自然历史博物馆的John Sparks博士获得了一笔赠款，用于研究Leiognathidae（ponyfishes）家族鱼类与发光海洋原核生物Leiognathi发光杆菌之间的进化、共同进化相互作用和共生现象。鱼类宿主丰富，经济重要，广泛分布于整个印度-太平洋地区。这种鱼在内部的食道周围结构（称为光器官）中拥有密集的细菌共生体，为细菌提供氧气和营养，并在与捕食，反捕食和性别特异性信号相关的各种显示中使用细菌发光。大多数ponyfish物种的男性表现出极大的扩大，结构复杂和物种特有的光器官，而女性的发展相对较差。据推测，雄性发光信号的性选择与光器官系统（LOS）的形态多样性和物种形成在ponyfish。虽然基于物种特异性雄性信号的性二态生物发光系统的进化和功能在萤火虫中有很好的记录，但在脊椎动物中，这些系统的了解很少。小马鱼为解决这些问题提供了一个很好的系统。利用DNA序列数据和鱼的LOS的表型特征，并根据共生关系模式进行研究，将重建小马鱼的进化关系。该项目将提供深入了解发光信号系统在鱼类的进化，性选择在ponfishes多样化的作用，在共生中，细菌是收购与每一代新的协同进化的相互作用，和共生的鱼和细菌的地理分布的作用。该项目将为系统学、共生、鱼类学、共同进化和鱼类地理学领域的博士后和学生参与者提供实地考察和培训。

A grant has been awarded to Dr. John Sparks of the American Museum of Natural History to examine the evolution, coevolutionary interactions and biogeography of the symbiosis between fishes of the family Leiognathidae (ponyfishes) and the luminous marine prokaryote Photobacterium leiognathi. The fish host is abundant, economically important, and widely distributed throughout the Indo-Pacific. The fish harbors a dense population of the bacterial symbiont in an internal circumesophageal structure, called a light organ, providing the bacteria with oxygen and nutrients, and uses bacterial luminescence in various displays associated with predation, anti-predation and sex-specific signaling. Males of most ponyfish species exhibit greatly enlarged, structurally complex and species-specific light organs, whereas those of females are comparatively poorly developed. It is hypothesized that sexual selection for male luminescence signaling is correlated with morphological diversification of the light organ system (LOS) and speciation in ponyfishes. Although the evolution and functions of a sexually-dimorphic bioluminescent system based on species-specific male signaling are well documented in fireflies, in vertebrates these systems are poorly understood. Ponyfishes provide an excellent system in which to address these questions. The evolutionary relationships of ponyfishes will be reconstructed using DNA sequence data and phenotypic features of the fish's LOS, and examined in light of symbiont patterns of relationship. This project will provide insight into the evolution of luminescence-signaling systems in fishes, the role of sexual selection in ponyfish diversification, coevolutionary interactions in a symbiosis in which the bacterium is acquired with each new generation, and the role of the symbiosis in the biogeographic distribution of the fish and bacterium. The project will provide exposure to fieldwork and training to post-doctoral and student participants in the areas of systematics, symbiosis, ichthyology, coevolution, and biogeography.