There has been significant concern regarding the global effects of climate change, especially on plant communities, which are influenced by individual plant species responses. Warming temperatures are having large repercussions for plant biodiversity, with rapidly changing environmental conditions causing shifts in species ranges and phenology. To better understand the implications of this phenomenon on plants, many studies have investigated responses of individual species to climate change. One approach that has grown in recent decades is the use of functional leaf traits, which are indicators of plant performance and reproductive capacity. Specific leaf area (SLA), the ratio of fresh leaf area to dry leaf mass, is one such trait that is attributed to plant growth and photosynthetic capacity, and found to be correlated with climate. We assessed the relationship between climate and SLA for Vaccinium ovalifoilum, a shrub that is prevalent in the montane ecosystems of Mt. Rainier. To accomplish this, we gathered SLA using samples from the Burke Museum’s herbarium collection whose distribution will be delineated across three elevational bands. Altitude was used as a proxy for climate due to variable environmental conditions found across elevation—namely temperature and precipitation—and the collection location of specimens allowed us to obtain temperature and snow accumulation data. With this information, we compared the variation between the three established elevational bands in which the specimens fell under. We hypothesized that as elevation increases, SLA will decrease, attributing this trend to a limited growing window to support high photosynthetic capacity as a result of later snowmelt and lower temperatures. Our results offered insight to understand how climate change may potentially affect plant functionality and guide future research to analyze how changes in individual species may influence community coexistence in the upcoming years.

Many plant species are known to undergo masting, where individuals within a species all produce a large amount of seed in a single year, with a sharp drop off in reproduction in the following years. Masting may be beneficial to plants by suppressing seed predator populations in low seed production years, allowing for seeds to escape predation in high seed production years. Masting is likely associated with climate, although this is poorly understood. In this study, I will use herbarium specimens to tackle questions related to masting in five plant species: Tsuga heterophylla, Pseudotsuga menziesii, Thuja plicata, Rubus spectabilis, and Rubus parviflorus. Specifically, I will note the number of cones, seeds or berries on herbarium specimens, as well as specimen size and the year it was collected. I will use these data to 1) examine patterns of masting in focal species as compared to field data from Mount Rainier. I hypothesize that herbarium specimens will show a similar pattern of masting as field data, with trees showing stronger patterns than shrubs. Next, I will use these data to 2) compare masting patterns to annual climate. I hypothesize that warm temperatures lead to masting the following year, and that masting has increased in frequency. Finally, I will 3) assess the relationship between masting and bird species that eat seeds and berries (e.g. grouse, jays), to determine whether masting influences population dynamics of higher trophic levels. I will do so by comparing masting patterns with bird count data from the Audobon Society. I hypothesize that population sizes of birds that rely on seeds and berries will be greater in mast years. This study provides additional information for how we might expect entire ecosystems to be affected by climate change, including resource distribution and population health.

Spatial variation in soil abiotic conditions at plant range limits may be important in determining how plant range limits will respond to climate change. One reason for this is that plants are known to change many characteristics of the soil around their roots in ways that influence the growth of other plants.The range limit of subalpine fir is expected to shift into subalpine meadows as the climate warms. Our goal for this project is to describe the abiotic soil qualities of a subalpine forest habitat and a subalpine meadow habitat on Mount Rainier to explore how these characteristics may affect the predicted range shift. We hypothesize that soils from subalpine meadows will have less organic matter and therefore less phosphorus, a lower carbon to nitrogen ratio, and less water holding capacity than soils from the subalpine forest. We will develop a protocol for measuring water availability and implement it on soil samples obtained from around the roots of subalpine fir trees in both the forest and meadow sites on Mount Rainier. We will use standardized tests to obtain the organic matter and phosphorus measurements. If our hypothesis of lower nutrient availability and water retention in meadow soils is supported, this may suggest that subalpine fir growing in the meadows have a greater dependency on fungal symbionts for obtaining soil resources. This would have important management implications given that suitable fungal symbionts are expected to be rare or absent at range limits.

p120 catenin is an adherens junction-associated protein responsible for stimulating both cell adhesion, through interactions with RhoA and E-cadherin, and cell motility through interactions with Vav-2 and Cdc-42/Rac-1. Recent research in vitro has identified selective phosphorylation as a regulation mechanism for which pathway p120 catenin undergoes, but the results have yet to be replicated in vivo. Here, I specifically focus on the effects of phosphorylation of the tyrosine at 228 (Y228) on dorsal axis extension in zebrafish embryos during embryogenesis. This was accomplished through co-injection of mutant mRNAs Y228E (glutamic acid) and Y228F (phenylalanine) alongside an anti-sense splice-site morpholino specific to p120 catenin δ1. When compared to uninjected embryos, embryos injected with Y228E and morpholino exhibited much poorer dorsal axis extension whereas embryos injected with Y228F and morpholino exhibited relatively normal dorsal axis extension. These findings suggest that phosphorylation of p120 catenin at Y228 promotes interaction with RhoA and E-cadherin, thus reducing interaction with Vav-2 and Cdc-42/Rac-1 and limiting cell motility, although the specific pathway is still unclear. I shall further validate these findings through co-precipitation of mutant p120 catenin and its binding partners by preforming immunoprecipitation (ReCLIP) of proteins obtained from developing injected zebrafish embryos. As loss of E-cadherin function is closely associated with cancer progression, the ability to facilitate E-cadherin function through phosphorylation of p120 catenin at Y228 suggests a novel method and area of study for combatting cancer.

The Hille Zebrafish Lab studies embryonic development and is particularly interested in cell motility and adhesion. We use zebrafish as a model organism due to its small size and rapid development, as well as for having clear embryos that allow researchers to observe somites form. One way that cells can crawl is through extending filopodia with actin microfilaments. The cell is anchored to other cells with adherens junctions and can push off against these anchor points, then form new adherens junctions with cadherin and other proteins. This method of walking is used for cells to move between other cells and is highly visible in premesoderm cell walking and somite formation. Cells need to regulate both elongation and adhesion, and a protein called p120 catenin activates both cadherins (which are needed for adhesions junctions) and the proteins RAC1 and CDC42 that stimulate motility through actin microfilament elongation and filopodia formation. Our hypothesis is that p120 catenins with phosphorylated tyrosines bind to Cadherins. In our mutant p120 RNA sequences, we test the activity of phosphorylatable residues by mimicking post-translational modifications with residues that can not be phosphorylated. For example, aspartic acid can mimic phosphorylated serine. Our lab has made and injected mutated mRNA sequences for p120 catenin to test if the mutant protein is able to rescue morpholino knocked-down embryos. We predict that if the tested amino acid is necessary for binding to a motility protein, then we will see rescue in phosphorylation mimics and no rescue in dephosphorylation mimics. My project was to make a p120 mutant that is missing most of the predicted regulatory amino acids. The truncated p120 sequence is called 4A and is a splice variant of wild type p120 that starts at the fourth methionine, omitting the regulatory region containing many phosphorylatabe sites.

Coevolution is a process where two or more species reciprocally affect each other's evolution over time. The traits of one species evolves in response to the other. This process can lead to the diversification of organisms with unique adaptive traits. Previous experiments tested whether coevolution occurred during the 2000 generations of evolution between the bacteria Desulfovibrio vulgaris and archaea Methanococcus maripaludis by pairing populations from 1000 generations with mutualist partners from their evolutionary past or future. Results suggested patterns of coevolution, but hypothesizing that those patterns occurred by accident, we tested whether or not patterns can occur that look like coevolution with microbes that could not possibly coevolve. We conducted a timeshifts control experiment using freezer stocks of D. vulgaris and M. maripaludis that evolved alone for 2000 generations and created pairings of the mutualists with five different generational pairings. They then were paired with an ancestral control group and a modern test group from the 1000th generation. Growth rates were calculated for each coculture. Graphs of the effects the 1000th generation of M. maripaludis and D. vulgaris had on coculture growth rate showed that M1000 had similar growth rates irrespective of its partners evolution while D1000 results were variable. An ANOVA test showed the mean log ratios statistically indistinguishable across all timepoints, indicating that the null hypothesis should be accepted. This result suggests that both partners have the same effects on fitness no matter how long they evolved. However, due to variations in results between D. vulgaris and M. maripaludis it is still unclear whether these populations have the ability to create patterns of coevolution due to their adaptation to their abiotic environment.