CALIFORNIA STATE UNIVERSITY, SACRAMENTO
My lab focuses on ecological divergence in marine intertidal habitats at a variety of spatial scales. We integrate next-generation sequencing techniques with phenotypic, genetic and biochemical assays to interpret large genomic datasets from a functional perspective.
My lab focuses on ecological divergence in marine intertidal habitats at a variety of spatial scales. We integrate next-generation sequencing techniques with phenotypic, genetic and biochemical assays to interpret large genomic datasets from a functional perspective.
CURRENT WORK:
Repeated Tissue Sampling to Correlate Gene Expression and Heat Stress Survival in the Marine Snail Chlorostoma funebralis Previous studies have demonstrated that southern California populations of the intertidal marine snail, Chlorostoma funebralis, have higher thermal tolerance than northern populations (see below, Gleason and Burton 2013). In addition, 222 genes were found to have a significant correlation between the probability of reaching 27°C in the field, the temperature that first causes a heat shock response in C. funebralis, and constitutive, baseline gene expression patterns that likely pre-adapt southern populations to frequent heat stress (see below, Gleason and Burton 2015, 2016). However, whether expression of these 222 genes correlates with heat stress survival within single individuals has not been investigated. The goal of this project will be to develop a protocol for taking nonlethal, repeated tissue samples of epipodial tentacles in northern and southern California individuals before, during, and after heat stress. Ultimately, the development of this tissue sampling technique will allow the correlation of gene expression data and survival data in single C. funebralis individuals. This will give us further insight into which candidate genes allow southern California populations to be thermally tolerant. COMING SOON: Assessing Phenotypic Effects of Heat Stress and Starvation in the Economically Important Red Abalone, Haliotis rufescens This work will enhance our understanding of the conditions that induce mortality and reduced growth during El Niño years in a sensitive early life stage of H. rufescens, an economically important California shellfish species. Juvenile red abalone will be subjected to three sets of experiments assessing mortality and growth under 1) heat stress, 2) starvation, and 3) combined heat stress and starvation conditions. |
POSTDOC
My postdoctoral work examined the biomechanical causes and biochemical consequences of individual‐scale variation in body temperature in intertidal mussels (Mytilus californianus).
|
3) JUVENILE THERMAL TOLERANCE PLASTICITY
Previous work has demonstrated substantial adult plasticity in sublethal physiological metrics that vary between intertidal sites (Jimenez et al. 2016); however, little is known regarding the roles of developmental plasticity vs. physiological constraint in the thermal tolerance of juvenile M. californianus mussels. Our results imply substantial, environmentally driven, developmental plasticity in both thermal tolerance and growth rate among recent mussel recruits from Hopkins Marine Station in Pacific Grove, CA. However, we found no evidence for analogous plasticity in adults from the same intertidal locations. (Gleason et al., 2018)
|
PH.D.
The research project for my dissertation took advantage of molecular genetic approaches to examine questions in ecology and evolution. My primary interests included the factors that affect the balance between local adaptation and the rate of interpopulation gene flow and the molecular mechanisms involved in responses to abiotic stressors in the environment. I investigated these questions regarding local adaptation in the sea using the intertidal marine snail Chlorostoma funebralis. Overall, my work not only provided insight into fundamental questions in ecological genomics, but it also enhanced our understanding of the potential impact of global climate change on marine invertebrates.
1) The first chapter of my dissertation used phenotypic assays to demonstrate that despite the fact that C. funebralis has a planktonic larval stage, following common garden acclimation southern California populations have a higher thermal tolerance than northern California populations. Southern populations suffer significantly lower mortality and recover significantly more quickly following heat stress compared to northern populations (Gleason and Burton 2013). |
3) To understand better why this gene expression strategy of pre-adaptation might be beneficial, I also examined in situ regional patterns of thermal stress by deploying "robosnails" (empty snail shells with iButton temperature loggers inside) at each of my six collecting sites. Field data suggest that southern, but not northern, snails experience temperatures that induce mortality, and that the probability of reaching a temperature that induces the heat shock response is three times higher in southern vs. northern California (Gleason and Burton 2016). |
2) To investigate the role of gene regulation in this ecological adaptation of C. funebralis, I employed a next-generation RNA-sequencing approach. The data demonstrate that both up-regulation and pre-adaptation of genes may be employed in evolutionary adaptation to thermal environments. Moreover, the data also suggest populations differ with regard to which mechanisms have evolved for specific sets of genes (Gleason and Burton 2015). |
4) Lastly, to increase our understanding of the dynamics influencing this adaptive divergence in C. funebralis, I used ddRAD-sequencing to identify 2371 genome-wide, quality filtered SNP loci in individuals collected from all six sites. Considering all SNP loci, there was no evidence for genetic differentiation among regions. However, outlier tests revealed 34 loci putatively under divergent selection between northern and southern populations. Three of these annotated outliers are known or hypothesized to be involved in stress granule formation. Given their multitude of cellular stress survival functions, the formation of these stress granules could be under selection in northern and southern California populations due to the differences in environmental thermal stress they encounter (Gleason and Burton 2016). |