Abstract:

Evolution of many eukaryotic organisms is affected by interactions with microbes. Microbial symbioses can ultimately reflect host’s diet, habitat range, and even body shape. However, how these intimate associations shape over evolutionary time is still elusive. A group of marine oligochaetes have no mouth, gut and excretory systems. Instead, these ‘gutless’ worms are packed with a suite of bacterial symbionts, including sulfate-reducing bacteria, sulfide-oxidizing bacteria and a spirochaete, which in concert provide the host with carbons and recycle host waste products. To better understand the evolutionary dynamics of this multi-partner symbiosis, this work focused on microevolution of the host and its symbionts in populations of the best-studied species, Olavius algarvensis. Metagenomes of hundreds specimens collected from several bays off the Island of Elba, Italy, and Mallorca, Spain, were analyzed based on single nucleotide polymorphisms in host nuclei, host mitochondria, and symbionts. Results showed that O. algarvensis forms reproductively well-isolated populations at a small geographic scale (~5 km), while variable mixtures of mitochondrial lineages co-occur and interbreed within each population. Compositions of symbiont species and intraspecific strains are highly linked to the host mitochondrial lineages, indicating their vertical co-inheritance along mitochondria, with symbiont members undergoing stochastic loss and replacement with symbiont-specific rates. A set of heritable symbiotic consortia unique to each location (i.e., host population) highlights that coevolution between gutless worms and their symbiotic consortia is likely a highly complex and dynamic process. This insight at a fine microevolutionary scale is applicable to evolutionary dynamics of other intimate animal-microbial symbioses.

Bio:

Yui is a postdoctoral fellow in James Cook University, and has joined the force for the Reef Restoration and Adaptation Program. His current work focusses on the effect of coral genetic diversity in the coral aquaculture effort and development of scalable detection methods for coral pathogens and pests using molecular approaches. Yui has completed his PhD in James Cook University on the ecology and microbiology of a coral disease. Following his PhD, he has conducted a postdoc fellowship on a closely related study in AIMS, and held a scientist position at the Max Planck Institute for Marine Microbiology until recently. In the Max Planck Institute, he used population-scale metagenomics to tackle evolutionary questions in animal-bacterial symbioses. The seminar outlines some of the highlight from this work in the MPI.