Higher genotypic diversity and distinct assembly mechanism of free-living Symbiodiniaceae assemblages than sympatric coral-endosymbiotic assemblages in a tropical coral reef

• Published in: Microbiology spectrum 2024-08, Vol.12 (8), p.e0051424
• Main Authors: Lin, Sitong, Li, Ling, Zhou, Zhi, Yuan, Huatao, Saad, Osama S, Tang, Jia, Cai, Wenqi, Yu, Kefu, Lin, Senjie
• Format: Article
• Language: English
• Subjects: Animals; Anthozoa - genetics; China; Coral Reefs; deterministic processes; Dinoflagellida - classification; Dinoflagellida - genetics; Dinoflagellida - physiology; diversity; Environmental Microbiology; ex hospite Symbiodiniaceae; Genetic Variation; Genotype; in hospite Symbiodiniaceae; ITS2; Phylogeny; Research Article; stochastic processes; Symbiosis; Sympatry
• ISSN: 2165-0497; 2165-0497
• DOI: 10.1128/spectrum.00514-24

While Symbiodiniaceae dinoflagellates are essential for coral health, ambient free-living counterparts are crucial for coral recruitment and resilience. Comparing free-living and Symbiodiniaceae communities can potentially provide insights into endosymbiont acquisition and recurrent recruitment in bleaching recovery. In this study, we studied coral-endosymbiotic and ambient free-living Symbiodiniaceae communities in the South China Sea. We collected samples from 183 coral and ambient plankton samples and conducted metabarcoding to investigate the diversity distribution, driving factors, and assembly mechanisms of the two groups of Symbiodiniaceae. Results revealed C1 and D1 as dominant genotypes. We detected a higher genotypic diversity in free-living than symbiodiniacean communities, but with shared dominant genotypes. This indicates a genetically diverse pool of Symbiodiniaceae available for recruitment by corals. Strikingly, we found that the cooler area had more Symbiodiniaceae thermosensitive genotypes, whereas the warmer area had more Symbiodiniaceae thermotolerant genotypes. Furthermore, and free-living Symbiodiniaceae communities were similarly affected by environmental factors, but shaped by different assembly mechanisms. The communities were controlled mainly by deterministic processes, whereas the ambient communities by stochastic processes. This study sheds light on the genetic diversity of source environmental Symbiodiniaceae and differential assembly mechanisms influencing Symbiodiniaceae inside and outside corals.IMPORTANCESymbiodiniaceae dinoflagellates play a pivotal role as key primary producers within coral reef ecosystems. Coral-endosymbiotic Symbiodiniaceae communities have been extensively studied, but relatively little work has been reported on the free-living Symbiodiniaceae community. Conducting a comparative analysis between sympatric coral-endosymbiotic and free-living Symbiodiniaceae communities can potentially enhance the understanding of how endosymbiont communities change in response to changing environments and the mechanisms driving these changes. Our findings shed light on the genetic diversity of source environmental Symbiodiniaceae and differential assembly mechanisms shaping free-living and Symbiodiniaceae communities, with implications in evaluating the adaptive and resilient capacity of corals in response to future climate change.