The population structure of species occupying deep-sea hydrothermal vents is strongly influenced by geological processes. The formation and maintenance of vents can create a patchwork of habitats across the sea floor, which are subject to catastrophic events that can extirpate whole communities. Therefore, the population structure of vent species is not only influenced by adaptation, life history, and dispersal but also by geological processes and oceanographic processes. Characterizing the genetic diversity and connectivity of species between vents can provide information about these processes. The Axial Seamount, located on the Juan De Fuca Ridge located off the Pacific Northwest coast of the USA, is a well-studied hydrothermal vent system. Here, sulfide worms (Paralvinella sulfincola) can be found on and around chimney vents, building tubes that contribute to chimney formation and habitats for other organisms. We predict low gene flow and low connectivity between different vent populations of this species because their reproductive life history strategies depend on pheromone signaling. Such signaling likely results in individuals mating more frequently with their closest conspecifics. However, little is known about the larval dispersion dynamics of this species. Sulfide worms were collected to investigate the connectivity and genetic diversity of their populations. Mitochondrial and nuclear genes were amplified from DNA extracted from worms that were collected from two locations within the Axial Seamount (Inferno and El Guapo chimneys, located within the ASHES and International District vent fields, respectively), to determine genetic diversity at each site and to test whether these sites constitute one or two separate populations. This research will ¬¬¬¬assist in understanding the connectivity and genetic diversity of sulfide worms within the Axial Seamount system across multiple vent fields and contribute to a broader understanding of how populations are established and maintained in this unique and dynamic ecosystem.

Describing genetic variation in deep-sea organisms is key to understanding ecological and evolutionary processes shaping biological diversity in these fragile ecosystems that are vulnerable to anthropogenic activity. Among deep-sea species, tubeworms (Class Polychaeta) often dominate faunal biomass in hydrothermal vents where they tend to grow in towering colonies. As foundation species, tubeworms create structural habitats that support assemblages of diverse biological communities across the seafloor. However, heterogeneous environmental conditions throughout their range, such as pH and temperature, and geographic isolation, may cause population subdivision by restricting connectivity between sites. This study aims to further our understanding of tubeworm population structure by investigating genetic relationships between Ridgeia piscesae subpopulations within a deep-sea hydrothermal vent system. At the Axial Seamount, a regularly surveyed area in the study of hydrothermal vent processes on the Juan de Fuca Ridge, our knowledge of the genetic connectivity of R. piscesae subpopulations remains limited. Here, we examined genetic variation in R. piscesae individuals collected from structurally-different sites within the Axial Seamount. Specifically, we genotyped mitochondrial genes and constructed SNP-based phylogenetic trees to elucidate evolutionary relationships between worms inhabiting a chimney and diffuse-flow locations. Genetic differentiation is expected to be low when gene flow is high between populations, but these outcomes may also be influenced by other aspects, such as environmental conditions. These results allow us to evaluate the degree of genetic diversity in tubeworms within this important area and provide insight into the potential impact of human activities, such as seabed mining, on deep-sea vent dynamics.