Larval dispersal capacity and realized connectivity: integration of physical transport models, larval plasticity, and gene flow in the north central Pacific

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Many important marine species live on or attached to the bottom of the ocean as adults, and they move between places and colonize new areas during microscopic larval stages that drift with ocean currents. Most larvae are too small to find or track in the ocean, so we know little about how long larvae can survive and how fast they grow under natural conditions. This limits our ability to understand how marine species colonize remote habitats, or how much potential there is for long-distance gene exchange that can help populations adapt to changing conditions in the sea. Because larvae are so hard to follow, their movement is often estimated indirectly from transport models of ocean currents and analyses of shared genetic variation among populations. These approaches are rarely combined, however, and the larval component of transport models is often based on unrealistic estimates of how long larvae can stay viable. This project is simultaneously generating estimates of larval dispersal from population genomic modeling and transport models of larval movement. The larval movement models are grounded in data from larval rearing experiments that mimic the natural food and temperature conditions that larvae experience in the North Central Pacific. The combined approach is helping explain how marine species colonize and persist in very isolated island areas and how likely they are to exchange genes across vast oceanic distances. The project is providing interdisciplinary training for three graduate students and several undergraduate research assistants. In addition, the investigators are partnering with a science outreach coordinator to engage Hawaiian high school students in field and lab work. This activity is aligning educational goals and assessments with a culture-and place-based framework for science education, Nā Hopena A‘o (HĀ), developed by the Hawaii Department of Education.The central goal of this project is to understand rates and patterns of long-distance connectivity between the Hawaiian archipelago and other remote island chains of the tropical north central Pacific. Specifically, the investigators are integrating empirically-derived data on larval life histories, biophysical transport models, and population genetic inferences about gene flow to understand how patterns of dispersal and connectivity in marine systems are affected by the capacity of larvae of many species to prolong development and delay metamorphosis. They are measuring planktonic larval duration under environmentally relevant conditions to test the capacity of larvae to extend development in the dispersal pathways leading to and from the Hawaiian Islands. Results from these laboratory experiments, as well as water-column data gathered over the past two decades, will be used in larval transport models that incorporate estimates of temperature, food availability, and varying life-history traits. Population genomic data gathered from the same species in the field will assess the role of gene flow in shaping genomic structure between Hawai'i and other isolated archipelagos and islands in the region, identify larval dispersal pathways to and from Hawai'i, test contrasting historical models of gene flow, and estimate rates of larval dispersal in and out of Hawai'i. This project is jointly funded by the Biological Oceanography Program and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.