Trophically transmitted parasites as “cross-taxon surrogates” of biodiversity in coastal environments

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)

Christopher Scott Moore (Creator)

Institution

East Carolina University (ECU )

Web Site: http://www.ecu.edu/lib/

Abstract: Parasitism is a highly successful life history strategy, and estimates suggest that as much as 40% of life on earth is parasitic. Healthy ecosystems have high parasite diversity, which in turn reflects underlying patterns of host diversity. Cumulatively, these host-parasite interactions span multiple trophic levels and are sensitive to disturbance, making trophically transmitted parasites useful as conservation tools for addressing a multitude of applied and theoretical questions. The four chapters in this dissertation advance the theory and practice of using trophically transmitted parasites as cross-taxon surrogates of biodiversity. Parasite diversity in key host species was used to assess overall community diversity, habitat heterogeneity, and ecosystem restoration outcomes in the short-term (<1-year) and up to 25 years following the addition of structured habitat. Chapter 1 quantifies the population structure of the naked goby (Gobiosoma bosc), a species of fish that likely serves as a key host within host-parasite food webs in the Pamlico and Neuse rivers. There is extensive gene flow among populations of gobies, although there is also evidence of local adaptation as evidenced by the frequency of unique haplotypes. Interestingly, parasite diversity in these fish appeared to be greater in areas with intact natural habitat, in contrast to anthropogenically-modified areas, an observation that became the focus of Chapter 2. For this work, infra-communities of digenetic trematodes were sampled from the eastern mudsnail (Ilyanassa obsoleta), a key host for trematode parasites in intertidal marine environments. Trematode community richness, evenness (Pielou’s), and diversity (Shannon, Simpson) were greater in snails sampled from natural shorelines with complex habitat (e.g., oyster reefs, saltmarsh cordgrass) as opposed to shorelines artificially reinforced with bulkhead structures. There were also important differences at the community-level that likely reflect underlying patterns of host diversity at different shoreline types. For example, the trematodes Lepocreadium seterifoides (LS) and Zoogonus lasius (ZL) were the most common species sampled across all sites, although they dominated parasites communities in artificial shorelines. Polychaetes serve as intermediate hosts for LS and ZL, taxa that are ubiquitous but more common in polluted or habitat-poor environments. On the other hand, the trematode HQ, which requires mollusks and shorebirds as hosts, was only found at sites with natural shorelines, suggesting that these areas are less disturbed and have a greater diversity of taxa serving as intermediate hosts. Chapters 3 and 4 expand on the role of habitat by testing the short and long-term response of the host-parasite community to ecological restoration. Chapter 3 used parasite diversity in common intermediate hosts to assess how traditional forms of habitat restoration (e.g., shell bags) compared to novel methods (e.g., Oyster Catchers™) in the short-term (< 1-year) following restoration. Relative to areas with bare mud flats, most host-parasite taxa groups increased in response to the presence of structure, although habitat complexity (i.e., oyster density) mattered less than the overall volume of habitat added to the system. There were also clear shifts in the functional diversity of species present in the community from more generalist taxa (e.g., grass shrimp, naked gobies) to reef-resident organisms (e.g., striped blennies, snapping shrimp). However, in the short-term following restoration it can be difficult to determine whether organisms are responding to the presence of added structure or the disturbance posed by the restoration itself. Chapter 4 used parasite diversity as a tool to evaluate long-term patterns of community succession in restored oyster reefs (5 to 22 years old). In general, the diversity of free-living taxa was highly variable and did not differ among New-Restored (<10 years), Old-Restored (>20 years), and Natural reefs. Conversely, parasite diversity increased with elapsed time post-restoration, and parasite communities in older restored reefs were more similar to those found in natural reefs. In addition, oyster toadfish (Opsanus tau) were identified as a key host species capable of facilitating parasite transmission and trophic ascent in oyster reefs food webs. According to the parasite data, trophic complexity in restored oyster reefs required at least 10 years to resemble that found in natural reefs. Altogether, this dissertation adds to a growing body of evidence demonstrating how parasites can serve as conservation tools. It also advances the rationale for using trophically transmitted parasites as biodiversity surrogates. Surrogate species in biodiversity monitoring studies must be capable of predicting the presence of other, more elusive taxa. Preference should be given to taxonomic groups from different trophic levels, especially cross-taxon surrogates that represent the functional links between organisms. Trophically transmitted parasites are ideal cross-taxon surrogates of biodiversity and trophic complexity, particularly when parasite diversity can be quantified in one or more key host species.

Additional Information

Publication

Dissertation

Language: English

Date: 2023

Subjects

parasite diversity, trophic complexity, ecological restoration, oyster reefs, community assembly, environmental monitoring

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