Facultative lifestyle drives diversity of coral algal symbionts

Trends Ecol Evol. 2024 Mar;39(3):239-247. doi: 10.1016/j.tree.2023.10.005. Epub 2023 Nov 10.

Abstract

The photosynthetic symbionts of corals sustain biodiverse reefs in nutrient-poor, tropical waters. Recent genomic data illuminate the evolution of coral symbionts under genome size constraints and suggest that retention of the facultative lifestyle, widespread among these algae, confers a selective advantage when compared with a strict symbiotic existence. We posit that the coral symbiosis is analogous to a 'bioreactor' that selects winner genotypes and allows them to rise to high numbers in a sheltered habitat prior to release by the coral host. Our observations lead to a novel hypothesis, the 'stepping-stone model', which predicts that local adaptation under both the symbiotic and free-living stages, in a stepwise fashion, accelerates coral alga diversity and the origin of endemic strains and species.

Keywords: Symbiodiniaceae; facultative lifestyle; genomics; stony corals; symbiosis.

Publication types

  • Review

MeSH terms

  • Animals
  • Anthozoa* / genetics
  • Biodiversity
  • Coral Reefs
  • Dinoflagellida* / genetics
  • Ecosystem
  • Symbiosis / genetics