Meeting Abstract
Host-symbiont interactions often form the foundation for ecosystem function and diversity around the world. One especially important relationship is the cnidarian-dinoflagellate endosymbiosis that exhibits exceptional flexibility, forming coral reefs while also extending into temperate latitudes. This diversity also extends to the molecular level, where genotyping techniques have revealed that the dinoflagellate symbionts Symbiodinium sp. can be classified into 9 major clades using the molecular marker ITS2. However, much less is known about within-clade variation, which ITS2 largely fails to resolve. Genetic loci that provide more resolution (microsatellites) produce patterns suggesting that within-clade symbiont populations can specialize on different environmental conditions, geographic locations, and host species. It is now possible to survey loci across the entire genome to determine the relative impact of these forces on Symbiodinium populations. Here, I use a genome-wide SNP dataset to explore the genetic structure of Symbiodinium sp. (all from Clade B) populations that form partnerships with three sympatric species of anemone in the genus Anthopleura along the Pacific coast of North America. First, I show that symbiont populations separated by hundreds of km are highly genetically differentiated, and within each locality, symbionts are further genetically differentiated by host species. Second, I identify signatures of adaptation in symbiont subpopulations that correlate with abiotic conditions across several degrees of latitude, a crucial step in determining the contributions of both hosts and symbionts to the performance of the holobiont across temporally and spatially heterogeneous environments.
