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

NSF Award Abstract

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 mostly through a microscopic larval stage that drifts 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 islands like the Hawaiian archipelago, 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 ocean current transport models 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. Our project will simultaneously generate estimates of larval dispersal from population genomic modeling and transport models of larval movement. These larval movement models will be grounded in data from larval rearing experiments that mimic the natural food and temperature conditions that larvae experience in the North Central Pacific. This combined approach will help us understand 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 will provide interdisciplinary scientific career training for three graduate students and several undergraduate research assistants. The PIs will work with an established science outreach coordinator who will partner our labs with high school groups who will participate in field and lab work. We will align 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. We will measure 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. Data from laboratory experiments will be used to parameterize larval transport models. Custom models that couple temperature and satellite-derived estimates of food availability will allow larval life-history traits to vary depending on available water column data gathered over the last ~20 years. Population genomic data gathered from the same species will be used to 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. By integrating empirically-derived data on larval life histories, biophysical transport models, and population genetic inferences about gene flow, this project has the potential to transform the fields of larval biology and marine connectivity with empirical tests of 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.