Award: OCE-1459546

The Role of Larval Orientation Behavior in Determining Population Connectivity Understanding the patterns, causes and consequences of larval dispersal is a major goal of 21st century marine ecology. Patterns of dispersal determine the rates of larval exchange, or connectivity, between populations. Both physical factors (e.g., water movement) and biological factors (e.g., larval behavior) cause variation in population connectivity. Population connectivity, in turn, has major consequences for all aspects of an organism?s biology, from individual behavior to metapopulation dynamics, and from evolution within metapopulations to the origin and extinction of species. Further, understanding population connectivity is critical for thedesign of effective networks of marine reserves – vital tools in the development of sustainablefisheries and to create resilience to climate change. Over the last decade, three distinct approaches have emerged as the leading contenders to provide the greatest insights into the causes of variation in population connectivity. First, direct genetic methods use parentage analyses to trace recruits to specific adults and observepatterns of connectivity. Second, coupled biophysical models make assumptions about water flow, larval ecology and behavior to predict patterns of connectivity. Third, studies of orientation behavior and sensory biology of late stage larvae suggest that the larvae might influence patterns of connectivity. Despite advances, it is still hard for biophysical models to accurately predict patterns of connectivity, suggesting that a better understanding of the ontogeny of larval sensory systems and orientation behavior is required so that it can be incorporated into these models and close the gap between observations and predictions of connectivity. The overall objective of this proposal was to conduct an integrated investigation of the development of larval sensory systems and orientation behavior in one tractable system: the neon goby, Elacatinus lori, on the Belizean Barrier Reef. There were three motives for this choice of study system. First, we had used direct genetic methods to describe the larval dispersal kernel for this species, and developed a coupled biophysical model for the region that predicted that the dispersal kernel should be more extensive than is observed. To our knowledge, this was the only system where the magnitude of the discrepancy between predictions of biophysical models and observations from genetic analyses was known. Second, we had developed a protocol for rearing larvae, providing a reliable source of larvae of all ages for the proposed experiments. Third, we had piloted the use of a Drifting In Situ Chamber (DISC), demonstrating that we could measure the orientation of larvae in the field. Intellectual Merit. The proposed research had three specific objectives. Objective 1)To Investigate ontogenetic changes in larval orientation capabilities. We used a variety of methods to study the development of larval sensory anatomy, providing a detailed description of the development of the olfactory, gustatory, auditory, mechanosensory and visual systems in these gobies. This work provides new insights into how these sensory systems might be used in orientation behavior. We used the DISC to study the development of larval orientation behavior, showing that, remarkably, larvae are able to orient soon after hatch.Objective 2)To investigate how larval orientation varies with environmental context.Further, we usedthe DISC to study the effects of environmental context on orientation behavior, showing that in deep water, near to the reef, larvae orient against the current. We incorporated these behaviors into a simple simulation model, revealing that they may help to explain the restricted dispersal kernel of this species. Objective 3)To test alternative hypotheses to identify the goal of larval orientation.We developed a rigorous experimental framework for testing and discriminating among alternative hypotheses for where larvae are heading, e.g., toward the natal reef or the nearest reef. This conceptual framework will facilitate future research investigating the goal of larval orientation. The results of this project are ground breaking in their own right, and they lay the foundation for a unique integration, using coupled biophysical models to predict patterns of dispersal and connectivity in the future. Broader Impacts. 1) Integration of research and teaching. The grant supported multiple postdocs and graduate students. They were trained in sensory anatomy, animal behavior and biological oceanography. Two of these trainees have gone on to further postdocs and two have completed their PhDs. PIs incorporated findings into their undergraduate and graduate courses. PI Buston received the Dean?s Award for Excellence in Graduate Education from Boston University. PI Paris received the 2018 AGU Rachel Carson Lecture Award. 2) Broadening participation of underrepresented groups. The grant supported many undergraduates recruited from groups traditionally underrepresented in STEM fields, and many of these have gone on to careers in STEM. 3) Broad Dissemination to enhance public understanding. Results were broadly disseminated to the scientific community and general public via publications in good journals, presentations at national and international conferences and press releases. Last Modified: 06/24/2019 Submitted by: Peter Buston