This project investigates how the external environment shapes the immune system. Seahorses provide an ideal model for studying host-microbe interactions for three reasons. The genetic structure of their immune system is simple. Also, their dispersal capability is limited, and their geographic distribution is broad. Previous research on the pot-bellied seahorse across its range in New Zealand and southeastern Australia found striking differences between the pattern of genetic diversity in those parts of the genome related to immune response versus those parts of the genome that are not under selection. This proposal aims to experimentally test field observations of host-microbe associations. It will address a key question in host-microbial co-evolutionary theory: Are host-microbe associations in natural populations a type of local adaptation for immunity? Marine environments provide an essential economic engine for food, transportation, commerce and recreation, but we still have a poor understanding of how human activities impact resident organisms and influence ecosystem health. The results of this research will be incorporated into the NSF-funded Authentic Research Experience in Microbiology program serving students at ten City University of New York campuses, and will inform marine conservation planning and management through the Ministry of Primary Industries, FishServe Commercial Fisheries Services, and the National Institute of Water and Atmospheric Research.
Host-microbe interactions are an underappreciated driver of adaptation. This project will evaluate a potential mechanism of local adaptation at the major histocompatibility class II locus (MHII) by testing the fitness consequences of host-microbe associations in the marine species Hippocampus abdominalis (the pot-bellied seahorse). Previous research on wild H. abdominalis across its geographic range detected enhanced levels of MHII variability at the population level relative to neutral loci. Sequencing of the host gut microbiome indicates that the local environment (urban, agricultural, or pristine) has a significant effect on the microbial composition of hosts collected from these sites. Experimental populations of H. abdominalis will be exposed to microbes showing positive, negative, or neutral associations with hosts in natural populations, and effects of MHII genotype on growth, condition, immune response and survival will be measured. The research proposed here represents an exciting opportunity to explicitly test field observations of host-microbe associations and targets a key evolutionary concept, microbe-mediated local adaptation, using an experimental protocol reflecting natural pathways of microbial exposure
