Phylogenetics, biogeography, and evolution of fishes

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The overall goal of my research program is to investigate evolutionary patterns and processes of biodiversity in fishes. I use phylogenetic trees as powerful tools to understand taxonomy and species diversity, the effects of geography and paleogeography on distributions and diversity, macroevolutionary consequences of shifts between habitat types, and adaptive evolutionary change. In the work proposed here, my research group will use cutting-edge genomic analyses to investigate lineages that underwent evolutionary transitions from marine to freshwater habitats in both North and South America. In North America, we will reconstruct the evolutionary history of the deepwater/fourhorn sculpin complex, a lineage that occupies deep and cold aquatic habitats. The deepwater sculpin is distributed in the deepest freshwater lakes of Canada, from Lake Ontario to Great Bear Lake, and is called a glacial relict because it likely originated when glaciers pushed marine waters into continental areas. Its closest relative is the marine fourhorn sculpin, distributed across the Arctic. Several populations of the fourhorn sculpin appear to have invaded freshwater lakes of the Canadian Arctic Archipelago, but their ancestry is unclear. To elucidate the relationships among these species and populations, we will collect data from sculpin genomes and infer lineage history. We will assess the role of glaciation in determining distributions and driving transitions between marine and freshwater habitats, and we will identify molecular changes associated with the invasion of freshwater. In South America, we will investigate American soles (Achiridae), a group of flatfishes that are mainly marine, but include freshwater species in the Amazon river, making them an excellent model system for studying the evolution of transitions between marine and freshwater habitats. To reconstruct the evolutionary history of achirids, we will build a phylogenetic tree based on sequences from >2000 genes. We will use the phylogeny to test how paleogeographic events drove habitat transitions and whether these transitions altered lineage and morphological diversification. We will also examine the evolution of genes involved in osmoregulation and visual adaptation to new environments. This research will illuminate the evolutionary causes and consequences of major habitat transitions. The work has implications for understanding community assembly, largescale patterns of species diversity, and how geographic events, including glaciation, sea level changes, and mountain building, affect biodiversity. Determining the genes associated with marine and freshwater habitats has relevance for aquaculture and fisheries biology. Understanding the evolutionary history and population structure of Canadian fishes is important for management and conservation. The ongoing effects of climate warming in the Arctic make understanding the biology of northern fishes and aquatic ecosystems a priority.