COLLABORATIVE RESEARCH: RUI: SINK OR SWIM: PHENOMIC AND TRANSCRIPTOMIC DIVERSIFICATION OF SCULPINS (TELEOSTEI: COTTIDAE) ENDEMIC TO LAKE BAIKAL, RUSSIA

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Ancient lakes are biodiversity hotspots, home to thousands of unique species with an extraordinary diversity of body forms and functions. With more than 1,500 species found nowhere else on the planet, Lake Baikal is an ideal environment to study the processes that resulted in creation of new species. The Baikal biodiversity hotspot is also a geographical anomaly, because global species diversity normally declines near polar regions. Despite Baikal's renown as the world's oldest, deepest, and largest lake, the evolutionary history of its unique species diversity remains poorly understood. This project examines the evolutionary history of sculpins, a group of primarily bottom-dwelling cold water fishes that colonized Baikal within a relatively short period of the lake's history. Baikal sculpins are uniquely adapted to life in an ancient lake, having evolved multiple open-water and deep-water forms. This project is focused on identifying the molecular basis for such variation, including gene sequences that evolve through generations and gene-expression changes that occur during development. New information gained from this study can be compared to ongoing research on fishes from other ancient lakes, in order to identify unifying processes that explain adaptation in these unique ecosystems.Baikal sculpins represent the world's northernmost vertebrate radiation within an ancient lake ecosystem, with at least 33 species estimated to have evolved within the past two million years. Rapid diversification of skeletal morphology and body composition suggests that this clade has undergone ecological release from a stream-living ancestor, but phylogenetic analysis has thus far been limited to a single genetic locus. A genomic inventory of Baikal sculpins will be generated through systematic surveys of all lake habitats and the surrounding watershed. Tributaries to Baikal will also be sampled in the search for a putative ancestral sculpin population. A time-calibrated species tree will be generated from sequence variants at presumed neutral (RADseq) and functional (RNAseq) loci. Gene expression phenotypes will be mapped on the phylogeny to infer relative rates of phenotypic and ecological change. If a putative ancestral population is discovered in the tributaries to Lake Baikal, this system will offer an unprecedented opportunity to understand the genetic factors that predispose certain groups to adaptive radiation.