Dispersal and the Evolutionary Landscape of Marine Parasitism

<jats:title>Abstract</jats:title> <jats:p>Parasites can exert strong selective pressures on their hosts, shaping the evolutionary trajectories of populations and species. In turn, parasites evolve in response to their hosts and their environments. In the ocean, where species disperse across a highly variable three-dimensional environment, both parasite transmission and host/parasite adaptation are fundamentally impacted by the movement of both parties. In this chapter, the author discusses the adaptive implications of marine dispersal and how it shapes the evolutionary landscape of parasitism in the sea over short timescales. This chapter focuses primarily on eukaryotic parasites, including pathogenic microparasites; horizontal gene transfer and other biological traits result in a substantially different evolutionary landscape for prokaryotic pathogens. The author briefly discusses dispersal in the sea generally and then more specifically the factors influencing marine parasite dispersal. Also, there is a brief discussion of long-distance, rare, or otherwise “extreme” dispersal of parasites. The author then moves into the influence of dispersal on adaptation in both hosts and parasites, with an extended case study on pesticide resistance in the salmon louse. Finally, some areas of particular interest for future research into marine dispersal and host–parasite adaptation are briefly suggested.</jats:p>