RESEARCH
This page highlights many of my current research interests, focal species, study systems, and different approaches to these questions/topics. It is constantly evolving (a good problem to have!) because I have several research projects at various stages (writing manuscripts, analyzing data, collecting data, developing new ideas, etc.).
I am excited to chat about possible projects and collaborations building off these ideas! Please contact me if you are interested (torrance.hanley [at] gmail.com).
OYSTER INTRASPECIFIC VARIATION
The eastern oyster (Crassostrea virginica) is a foundational species for reefs along the Atlantic and Gulf coasts of the United States. A global decline of oyster populations due to a variety of stressors — including overfishing, increasing temperatures and changing salinities, and altered predator-prey interactions and host-parasite dynamics — has resulted in more investment in and importance of aquaculture and restoration. I am studying how oyster intraspecific variation (genetic diversity, source identity, phenotypic variation) affects population dynamics, community interactions, and ecosystem functions on oyster reefs at different scales, and in turn, how this can inform best practices for restoration design and oyster aquaculture. For example…
How do different metrics of oyster intraspecific variation (cohort richness, genetic relatedness, etc) relate to oyster demographic traits (e.g., survival, growth, recruitment)? Do these effects of genetic variation on vital rates vary across environments (e.g., low/high predation intensity, resource availability, etc.)? Hanley et al. 2016 Ecology
How do characteristics of field-collected broodstock (e.g., male:female ratio, effective population size) and hatchery-produced juvenile cohorts (e.g., genetic diversity) affect trait variation and oyster performance across environmental conditions? Hughes, Hanley, et al. 2019 Ecological Applications
How does host intraspecific variation mediate parasite community structure? Specifically, how does oyster genetic identity (i.e., seed source) affect prevalence and intensity of micro- and macro-parasite species on experimentally-restored oyster reefs? Hanley et al. in review
I am starting a new project funded by Woods Hole Sea Grant looking at how aquaculture farming methods can mitigate the effects of oyster parasites/diseases and environmental micropollutants, as well as the combined effects of these stressors. (Collaborators: Dr. Loretta Fernandez, Dr. Jon Grabowski, Dr. Randall Hughes, Dr. David Kimbro)
SPARTINA LOCAL ADAPTATION
Spartina alterniflora (smooth cordgrass) is a foundational species in salt marshes across the United States, characterized by different growth forms (e.g., tall Spartina in the low marsh and short Spartina in the high marsh). The genetic and environmental factors underlying this fine-scale trait variation likely mediate plant-soil interactions that in turn affect the capacity of salt marshes to respond to sea level rise and anthropogenic stressors. I am exploring how Spartina intraspecific variation affects plant-microbial and plant-fungal interactions using a combination of field surveys, greenhouse experiments, and molecular techniques, with the goal of informing salt marsh management practices and restoration techniques. For example…
Is there evidence of repeated microgeographic genetic and adaptive phenotypic divergence in Spartina alterniflora? A field survey of genetic differentiation between short- and tall-form Spartina, combined with a greenhouse common garden and field reciprocal transplant suggests yes! Zerebecki, Sotka, Hanley et al. 2021 The American Naturalist
How does intraspecific variation in both plant growth forms and associated fungal strains affect fungal characteristics, plant traits, and plant-fungal interactions? A greenhouse inoculation experiment suggests that novel interactions as a result of unequal distributional shifts in response to changing environmental conditions may impact Spartina performance. Hanley et al. in revision
What are the short- and long-term effects of nutrient enrichment on Spartina alterniflora genotypes and associated microbial communities? A greenhouse common garden and field reciprocal transplant suggest that nutrient enrichment not only impacts plant foundation species and associated soil microbes in the short term, but also may have long-lasting effects that potentially compromise their ability to respond to changing resource conditions in the future. Hanley et al. 2021 Journal of Ecology
Here is the blog post that I wrote to accompany this paper - Journal of Ecology Blog
This study was also featured on the cover of Journal of Ecology Volume 109 Issue 11. Many thanks to Dr. Randall Hughes for this terrific photo, taken the day we ended the field reciprocal transplant experiment!
ZOSTERA GENETIC VARIATION
Zostera marina (eelgrass) is a foundational species in seagrass meadows along the east and west coasts of the United States that provides a variety of ecosystem functions and services, including nursery habitat for ecologically- and economically-important fish species, (blue) carbon sequestration, and coastal protection from shoreline erosion. Often, seagrass meadows span a depth gradient that corresponds to fine-scale variation in traits related to productivity (density, height, etc.), phenology (timing of flowering), and allocation (ratio of aboveground to belowground biomass, proportion of flowering vs vegetative shoots, etc.). These phenotypic differences may reflect underlying genetic structure and variation, be due to environmental characteristics, or a combination of both. I am interested in how the interplay of these factors across life history stages (seed, seedling, adult) reinforces trait variation and/or contributes to genetic differentiation across depths, with the goal of predicting how microgeographic adaptation may affect the health and stability of seagrass meadows given rising sea levels. For example…
Does genetic diversity affect eelgrass seed germination and/or seedling morphology and production? A greenhouse experiment manipulating seed genetic relatedness suggests yes! Hughes, Hanley, et al. 2016 Ecology
Does eelgrass density, morphology, and phenology vary across depths? A field survey of multiple meadows identified consistent differences in timing of flowering that may limit gene flow and contribute to genetic divergence across depths. von Staats^, Hanley^, et al. 2021 Estuaries and Coasts (^co-first authors)
I am currently collaborating with Dr. Cynthia Hays, Dr. Randall Hughes, and Dr. Erik Sotka on a NSF-funded project looking at eelgrass genetic structure and phenotypic variation across environmental gradients and life stages, with the goal of assessing presence/absence of patterns of local adaptation and microgeographic divergence to inform management and restoration of seagrass meadows.