Data from: New insights into the dynamics between reef corals and their associated dinoflagellate endosymbionts from population genetic studies.

The mutualistic symbioses between reef-building corals and micro-algae
form the basis of coral reef ecosystems, yet recent environmental changes
threaten their survival. Diversity in host-symbiont pairings on the
sub-species level could be an unrecognized source of functional variation
in response to stress. The Caribbean elkhorn coral, Acropora palmata,
associates predominantly with one symbiont species (Symbiodinium ‘fitti’),
facilitating investigations of individual-level (genotype) interactions.
Individual genotypes of both host and symbiont were resolved across the
entire range of the species. Most colonies of a particular animal genotype
were dominated by one symbiont genotype (or strain) that may persist in
the host for decades or more. While Symbiodinium are primarily clonal, the
occurrence of recombinant genotypes indicates sexual recombination is the
source of this genetic variation, and some evidence suggests this happens
within the host. When these data are examined at spatial scales spanning
the entire distribution of A. palmata, gene flow among animal populations
was an order of magnitude greater than among populations of the symbiont.
This suggests that independent micro-evolutionary processes created
dissimilar population genetic structures between host and symbiont. The
lower effective dispersal exhibited by the dinoflagellate raises questions
regarding the extent to which populations of host and symbiont can
co-evolve during times of rapid and substantial climate change. However,
these findings also support a growing body of evidence suggesting that
genotype by genotype interactions may provide significant physiological
variation; influencing the adaptive potential of symbiotic reef corals to
severe selection.