DISSERTATION RESEARCH: Investigating the role of specialist and generalist host associations in a multi-level sea anemone symbiosis

Ohio State University, The, Columbus OH

Investigators

Abstract

Symbiosis is an important driver of biodiversity and shapes all levels of biological organization. As a biodiversity hotspot, tropical coral reefs achieve much of their success and diversity from a network of multi-level symbioses. Although this reliance on symbiosis is well recognized, we know very little about how genetic diversity evolves within a symbiotic marine framework. Namely, our expectations surrounding resource specialization and co-diversification come primarily from the terrestrially biased literature, whereas discordant land-sea processes that act at the population level may lead to different outcomes. This research will test evolutionary hypotheses surrounding symbiosis and resource specialization by studying multiple crustacean species that all live on the corkscrew sea anemone on Caribbean coral reefs, yet vary in their host specificity. Using genomic DNA sequencing, the researchers will identify and describe previously unrecognized cryptic species, test whether increased host specificity leads to more incidences of speciation, and whether patterns of co-evolution can be recovered among these symbionts across the entire Caribbean. This research will train one graduate student and provide undergraduate students with research opportunities in the marine and molecular evolutionary sciences. Educational materials will be developed to demonstrate co-evolutionary principles in undergraduate biology courses, and public outreach events will target the ornamental aquarium trade as all study species are collected commercially. Resource specialization is expected to leave a strong signature on the genome and play an important role in species diversification. Species with narrow ecological requirements are expected to have smaller, more fragmented habitats, smaller effective population sizes, and ultimately, reduced neutral genetic variation compared to generalists. These expectations are broadly referred to as the specialist-generalist variation hypothesis (SGVH) and are an extension of classic population genetics theory. Within a symbiotic framework, host specificity should be especially useful for testing the expectations of the SGVH because micro-evolutionary processes coupled with symbiotic association will impact the population and evolutionary dynamics of each symbiont. Symbiosis generates an a priori expectation of shared biogeographic history and co-diversification, but variation in host specificity may lead to vastly different demographic histories and evolutionary responses to historical environmental conditions. Thus, the comparison of symbiotic taxa can potentially disentangle the extrinsic forces that effect whole communities from the intrinsic aspects of species biology, shed light on co-evolutionary processes and the emergence of the symbiosis. This research will use high-throughput genomic DNA sequencing and model-based coalescent analyses to delimit and describe cryptic crustacean lineages, examine the role of specialism and generalism on the evolution of genetic diversity, and explore patterns of co-diversification, demographic expansion, and community level phylogeographic breaks across the tropical Western Atlantic. This study will expand the taxonomic scope of the tropical, marine, phylogeographic literature and provide insight into the evolutionary processes that act on marine symbioses.