RAPID EVOLUTION OF THERMAL TOLERANCE AND GENOMIC DIVERGENCE DURING THE INVASION OF A PROLIFIC NON-NATIVE RED SEAWEED, Gracilaria vermiculophylla
Flanagan, Benjamin Allen
MetadataShow full item record
Biological introductions have rapidly increased during the 20<sup>th</sup> century and can negatively impact recipient communities by homogenizing biodiversity. Commonly, colonization success has been attributed to ecological and demographic processes, such as high growth rates or reproductive output. Recently, evidence suggests responses to the novel non-native environment through rapid evolutionary change(s) likely facilitates invasion success. Here, we used the widespread marine invader, <i>Gracilaria vermiculophylla </i>to study the role rapid adaptation plays in facilitating invasions. We observed rapid evolution in thermal tolerance and evaluated genome-wide evolutionary changes associated with the invasion. By exposing native and non-native thalli to extreme temperature and observing survival, we found non-native thalli have rapidly evolved higher thermal tolerance compared to native thalli. Additionally, by performing a targeted expression analysis, we observed non-native thalli induced two heat-shock proteins (Hsps) to higher levels than native thalli, suggesting a molecular mechanism underlying the rapid phenotypic shift in thermal tolerance. We also used Hsp inhibitors to arrest Hsp molecular function and these inhibitors compromised the ability of thalli to survive heat stress. To evaluate genome-wide evolution, we used genotype-by-sequencing techniques to identify approximately 9,000 single-nucleotide polymorphisms. We identified highly divergent loci between the invasion source region of northeastern Japan and non-native genetic subregions. The results suggest both neutral and non-neutral evolutionary processes shaped the invasion, but neutral evolutionary forces dominated. The combined phenotypic and genomic work of my thesis advances our understanding of the role rapid evolution plays in facilitating successful invasions.