Endosymbiotic flexibility associates with environmental sensitivity in scleractinian corals

Area of Science:

• Marine Biology
• Ecology
• Symbiosis Research

Background:

• Biological flexibility is crucial for ecosystem function and stability.
• Coral-Symbiodinium symbiosis is vital for coral reef health, with environmental thresholds impacting dinoflagellate communities.
• Symbiotic flexibility is proposed as a mechanism for coral adaptation to climate change.

Purpose of the Study:

• To investigate the flexibility of the coral-Symbiodinium symbiosis across various coral species and genera.
• To quantify Symbiodinium ITS2 sequence assemblages to assess symbiotic flexibility.
• To classify corals as generalists or specifists based on their symbiotic flexibility.

Main Methods:

• Quantification of Symbiodinium ITS2 sequence assemblages in different coral species.
• Development of a flexibility index based on phylogenetic divergence and relative abundance of Symbiodinium sequences.
• Comparative analysis of flexibility across coral genera.

Main Results:

• Profound differences in coral symbiotic flexibility were observed, leading to the classification of corals as generalists or specifists.
• Generalist corals (e.g., Acropora, Pocillopora) exhibit high flexibility but are environmentally sensitive.
• Specifist corals (e.g., massive Porites) show low flexibility, harbor narrow Symbiodinium assemblages, and are environmentally resistant.

Conclusions:

• Findings challenge the notion that symbiotic flexibility universally enhances holobiont resilience.
• The study highlights the need for further research into the functional benefits of endosymbiotic diversity and flexibility under environmental stress.
• Understanding coral symbiotic flexibility is critical for predicting reef responses to climate change.