Mutually beneficial interactions between microorganisms and animals are a conserved and ubiquitous feature of biotic systems. In many instances animals, including humans, are dependent on their microbial associates for nutrition, defense, or development. To maintain these vital relationships, animals have evolved processes that ensure faithful transmission of specific microbial symbionts betwee...

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We investigate the generation and decay of interspecific disequilibrium (ID) between organelle and symbiont genomes as a function of the rate of horizontal transmission. We show that rare horizontal transmission greatly diminishes the covariance between organelle and symbiont genomes. This result has two important implications. First, a low level of ID does not indicate low levels of vertical t...

The specific identity of endosymbiotic dinoflagellates (Symbiodinium spp.) from most zooxanthellate corals is unknown. In a survey of symbiotic cnidarians from the southern Great Barrier Reef (GBR), 23 symbiont types were identified from 86 host species representing 40 genera. A majority (.85%) of these symbionts belong to a single phylogenetic clade or subgenus (‘‘C’’) composed of closely rela...

Vertical transmission of obligate symbionts generates a predictable evolutionary history of symbionts that reflects that of their hosts. In insects, evolutionary associations between symbionts and their hosts have been investigated primarily among species, leaving population-level processes largely unknown. In this study, we investigated the tsetse (Diptera: Glossinidae) bacterial symbiont, Wig...

Chemosynthetic endosymbioses occur ubiquitously at oxic-anoxic interfaces in marine environments. In these mutualisms, bacteria living directly within the cell of a eukaryotic host oxidize reduced chemicals (sulfur or methane), fueling their own energetic and biosynthetic needs, in addition to those of their host. In habitats such as deep-sea hydrothermal vents, chemosynthetic symbioses dominat...

Bathymodiolus azoricus and Bathymodiolus puteoserpentis are symbiont-bearing mussels that dominate hydrothermal vent sites along the northern Mid-Atlantic Ridge (MAR). Both species live in symbiosis with two physiologically and phylogenetically distinct Gammaproteobacteria: a sulfur-oxidizing chemoautotroph and a methane-oxidizer. A detailed analysis of mussels collected from four MAR vent site...

Symbionts can have mutualistic effects that increase their host's fitness and/or parasitic effects that reduce it. Which of these strategies evolves depends in part on the balance of their costs and benefits to the symbiont. We have examined these questions in Wolbachia, a vertically transmitted endosymbiont of insects that can provide protection against viral infection and/or parasitically man...

It is unclear how mutualistic relationships can be stable when partners disperse freely and have the possibility of forming associations with many alternative genotypes. Theory predicts that high symbiont relatedness should resolve this problem, but the mechanisms to enforce this have rarely been studied. We show that African fungus-growing termites propagate single variants of their Termitomyc...