Highly diverse and geographically differentiated Symbiodiniaceae communities associated with the hydrocoral Millepora alcicornis in the Atlantic Ocean

The symbiotic relationship between corals and symbiodiniaceans can favor reef formation, but is easily rupted when these organisms are exposed to thermal anomalies. Here, we assessed the ITS2 rDNA phylotype diversity of dominant Symbiodiniaceae lineages associated with the hydrocoral Millepora alcicornis and investigated host–symbiont distribution patterns in the Atlantic Ocean. This is the first effort to assess the symbiont community of this hydrocoral over nearly its entire distributional range. Millepora alcicornis is highly generalist in the composition of its photosymbiont community. We found 16 ITS2 phylotypes, mainly of the genus Breviolum but also of the genera Symbiodinium and Cladocopium; nine of them are new lineages. The distribution patterns of the M. alcicornis–Symbiodiniaceae associations were explained by differences in primary productivity, photosynthetically active radiation, water turbidity, and temperature. Six geographic sections were identified. Colonies from the Brazilian Northeastern Region showed the most stable associations, with two Breviolum phylotypes, while those from the Brazilian Eastern Region showed the most diverse symbiont community, composed of three genera of Symbiodiniaceae. A new and dominant phylotype of Breviolum was identified in the Brazilian Southern Region. Our results suggest a radiation of Breviolum lineages associated with M. alcicornis through the Atlantic Ocean. The impressive diversity of symbiotic associations observed characterizes an adaptable host–symbiont relationship, which can be key for colonization of new habitats and the resilience of milleporids to environmental changes.

Citation

Garrido, A. G., de Assis Leite, D. C., Machado, L. F., Peixoto, R. S., & Zilberberg, C. (2022). Highly diverse and geographically differentiated Symbiodiniaceae communities associated with the hydrocoral Millepora alcicornis in the Atlantic Ocean. Coral Reefs. https://doi.org/10.1007/s00338-022-02266-3

Sponsors

We thank the Brazilian Marine Biodiversity Network SISBIOTA-Mar and Instituto de Pesquisas Coral Vivo for the collections, Dr. Guilherme Longo and Dr. Carlos Eduardo Ferreira for Curaçao sampling, MSc. Livia Peluso and Dr. Mariana Teschima for help with sampling and laboratory analysis, and Dr. Thiago Mendes for help with statistical analysis. We additionally thank two anonymous reviewers that greatly improved the final version of the manuscript. We thank the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA)/Chico Mendes Institute for Biodiversity Conservation (ICMBio), for the sampling permission (22387-1), in accordance with the Instruction Normative n° 03/2014 of System Authorization and Information on Biodiversity (SISBIO). This work was funded by the Conselho Nacional de Desenvolvimento Científico (CNPq) granted to CZ (423660/2016-0), Edital MCTI/CNPq Nº 01/2016 – Universal, and by a MSc fellowship to AGG.