Andrew W. Thompson
Evolution of Annualism in Killifishes: An Eco-Evo-Devo Approach
Michigan State University
Seminar Date: May 2, 2019
Annual killifishes inhabit seasonal pools that desiccate, resulting in the death of the adult population. Unique adaptations including specialized egg structures, desiccation resistance, and up to three diapause stages slowing developmental and metabolic rates enable the embryonic population to survive annual dry seasons. When the habitat floods, annual killifish terminate their third and final diapause (DIII), hatch, and begin a new lifecycle. Here we explore the genomics of embryonic DIII in annual killifishes. We use scanning electron microscopy, comparative transcriptomics, phylogenetic methods, and model rates of gene evolution to investigate the genetics of killifish annualism, diapause, and environmentally-cued hatching. We discover hundreds of candidate genes involved in diapause and delayed hatching in three killifish species. Specifically, we find 10 differentially expressed killifish transcripts with homologs also differentially expressed in the same direction during dormancy in other animals. These 10 transcripts illustrate the conserved roles of these homologs during delayed development in metazoans. Additionally, tight linkage of diapause and hatching with the expression of a complex family of hatching enzymes leads us to analyze regulatory mechanisms associated with environmentally-cued hatching. Lastly, we show that diapause has up to 7 origins in killifishes and detect over 160 genes with increased rates of molecular evolution in annual compared to non-annual killifishes. Our integrative framework combining development, genomics, evolution, and ecology provides important insights into the mechanisms of diapause and the diversity of vertebrate hatching strategies as well as candidate genes associated with stress tolerance in the face of changing environments.