Epigenetic regulation and local adaptation in marine mussels

Two populations of the marine mussel, Mytilus californianus, reside along the Oregon coast and experience marked differences in environmental and oceanographic conditions despite being only 65Km apart. Previous research suggests these populations experience high levels of gene flow resulting in genetically homogenous populations. As a result, it is assumed differences in physiological responses to environmental conditions are plastic and can be adjusted over time. Yet a number of studies have identified physiological differences that appear to be maintained for extended periods of time even under common garden conditions. This would suggest the potential for local adaptation exists within this broadly distributed species. In this study we used a reciprocal transplant design to examine these populations for signs of local adaptation by characterizing growth, gene expression, and global DNA methylation levels across populations. Our results indicated physiological plasticity cannot fully compensate for changes in growth conditions and that these populations may be adapted for optimal growth at the site from which they originated. These populations also displayed different levels of DNA methylation, which we postulate may provide a mechanism for local adaption to occur in these populations while maintaining genetic homogeneity.

Speaker: Sean Place, Sonoma State Univ