Meeting Abstract
All organisms depend on symbiotic interactions with bacteria for their success, yet little is known of the evolutionary processes that shape the specificity of these associations. Coral reef fish in the genus Siphamia form symbiotic associations with luminous bacteria, which they provision in a gut-associated light organ. There are 25 described Siphamia species that are distributed throughout the Indo-Pacific, however, the light organ symbionts of only a single host species, S. tubifer, from a small region in the Okinawan Islands, Japan have been described to date. Using Siphamia specimens archived in natural history collections and applying whole genome shotgun sequencing methods, the luminous symbionts of 15 host species were identified. Additionally, the light organ symbionts of S. tubifer specimens from locations representing their broad biogeographic distribution, ranging from eastern Africa to French Polynesia were described. Using targeted sequence capture methods, the phylogenetic relationships across the host genus were also inferred and compared to that of their luminous symbionts to test for evidence of co-divergence of host and symbiont. Results indicate that the bioluminescent symbiosis is highly conserved across the host genus; the light organ symbionts of all Siphamia species examined were identified as Clade II of Photobacterium mandapamensis, the luminous symbiont of S. tubifer that was previously identified. Furthermore, the association between S. tubifer and P. mandapamensis is highly conserved throughout the host’s broad Indo-Pacific distribution and through time. This high degree of specificity observed for this bioluminescent symbiosis suggests that the association could be genetically constrained at the genus level and presents the opportunity to investigate the genetic mechanisms regulating the specificity of host-microbe associations.
