Investigating interactions between climate, host life history and viral diversity across a trans-hemispheric range of marine ecosystems

Abstract

Marine infectious diseases and pathogens substantially impact the structure and function of marine communities by causing mortalities and altering host behaviors. The interactions between host and pathogen, determining the epidemiologicaloutcomes are affected by many factors including climate, host life history, and human activities. Studies on marine disease epidemiology and ecology, including both natural and anthropogenic transmission pathways, are necessary for better understanding how these factors potentially influence the host-pathogen interactions. A significant proportion of marine pathogens are viruses; they cause severe infectious diseases and mortalities in many marine organisms, including crustaceans. Virus-related diseases and mortalities have been identified and reported in the Atlantic blue crab, Callinectes sapidus, for more than half a century. With a wide geographic distribution across both hemispheres and a temperature-dependent variable life history, blue crab and its pathogenic viruses constitute a well-suited pathosystem for investigating the potential influences of climate, seasonality, and host life history on viral disease emergence and spread in marine ecosystems. This dissertations applied the "blue crab-virus” pathosystem, to investigate factors that potentially influence the interactions between blue crab and its viral symbionts. The studies mainly focused on three objectives: 1) Investigate the influences of climate, seasonality, and host life history on the prevalence and disease ecology of a virus that is pathogenic to blue crab. 2) Assess the influences of climate, seasonality, and host life history on viral genetic diversity and genetic structures across a wide spatial and temporal range. 3) Characterize genome sequences and biological characteristics of newly identified viruses in blue crabs. The studies encompassed in this dissertations demonstrate, in a single host species, that climate, temperature, and host life history traits drive patterns of virus species diversity and genetic variation across the entire range of the host. One significant revelation was the evidence of long-distance movement of virus pathogen genotypes by human transport of infected blue crabs between states in the United States. The dissertations concludes with a discussion of the potential for next-generation sequencing to discover and study the movement of known and newly discovered viruses in marine hosts.