In our latest post Graydon Gilles, MSc student at University of Queens, presents his work ‘Temperature-dependence and genetic variation in resource acquisition strategies in a model freshwater plant’. He explains the mechanisms behind competition, shows the challenges behind building a lab in your apartment and shares his passion for outdoor ecology.
About the paper
As temperatures increase because of anthropogenic climate change, organisms are going to be exposed to increasingly stressful temperatures. We’ve found that, with this increase in stress, competitors require even more resources just to keep growing, making them less likely to succeed in resource-poor environments. During my undergraduate degree at the University of British Columbia in Vancouver, I had the opportunity to work with Prof. Amy Angert and Dr. Takuji Usui to investigate how increasing temperatures affect the competitive ability of organisms. In environments where resources are limiting, theory suggests that the competitor that can maintain positive population growth at a lower resource level should outcompete the other. This trait that describes the minimum level of resources required for a population to grow is often called its R* (“R-star”). However, how a population’s R* might be affected by increased stress, or how much variation in R* exists among genotypes (i.e., different genetic lineages) of the same species, has not been well-studied. To answer these questions, we conducted an experiment to calculate R* for 11 genotypes of duckweed in the Lemna species complex. Duckweed are small, aquatic flowering plants that make a great system for studying questions about population growth in response to environmental conditions because they rapidly clone themselves, budding and detaching new ‘fronds’ within just a few days, and it is easy to manipulate the conditions they’re grown in. We grew populations in cups across a gradient of nitrogen concentrations to calculate their R* for nitrogen and exposed them to either ‘benign’ (room temperature) or ‘hot’ (~37˚C) treatments.
What we found is that these populations exhibited a large increase in their R* for nitrogen when exposed to hot conditions. In other words, when these populations were stressed, they required a much larger amount of resources just to maintain positive population growth. This suggests a mechanistic process by which higher temperatures may reduce a population’s competitive ability by increasing its resource demands. We also found a small amount of genotypic variation in R*, but this variation was further reduced when populations were exposed to heat, suggesting a reduced ability for selection to act on R* under stressful conditions.
Caption: Flasks sitting under grow lights containing stock populations of the 11 experimental Lemna genotypes that were used for seeding experimental populations (Credit: Graydon Gillies).
About the research
For me, this research project is a story of perseverance in science, as I was challenged by both the pandemic and failing experiments. I was in my undergraduate degree when I was originally offered a summer position in Prof. Angert’s lab in March of 2020 – just a week before the university announced a shut down and the transition to online schooling due to COVID-19. However, with some deliberation, the job still went forward, but it looked a little different than I expected as we dealt with the challenges of doing laboratory work remotely. Over the first couple weeks of that summer, my small studio apartment quickly transformed into a duckweed lab. My desk became a storage unit for our genotype library, my kitchen counter was converted into a lab bench, and I built shelving with grow lights to hold the many Erlenmeyer flasks of duckweed that I used to run preliminary experiments. It was an unconventional start to my first time doing science, but I’m grateful that I could still be involved during the pandemic. As mid-summer arrived, I was eventually granted limited access to the (real) lab and could start our full experiment.
However, running the experiment itself did not go smoothly. Half of our duckweed populations were exposed to a heat treatment, grown in cups suspended in large water baths with submerged heating rods fastened to the bottom. Unfortunately, our heat treatment worked a little too well, and most of our duckweed outright died. In some cups, the nutrient media completely evaporated, leaving behind a few sad, dried-up duckweed fronds. We attempted several fixes, such as re-calibrating the heating rods, reducing the number of rods in the bath, and playing with the water level, thinking we could get our experiment to work with the equipment we had. But, with a late start to the project, we ran out of time before we could pivot to something else, and it seemed that the project had failed.
The following summer, however, I was lucky to have the opportunity to take another job with the lab and try the whole experiment again. This time, we hit the ground running. I rebuilt our heat baths from scratch using new equipment, and carefully monitored the temperature. Thanks to the perseverance of our research group, we were able to collect usable data and I went on to write up the project with my co-authors. I learned that setbacks in science don’t always mean failure. While it can be frustrating to have experiments not work the first time around, sometimes it just requires the dedication to push through and find a different way to approach the problem. Not to mention, my mentors in the lab were always supportive of me throughout both experimental- and pandemic-related challenges, which instilled in me the drive to keep trying.
A heated water bath used in the experiment, containing cups with growth media and duckweed populations (Credit: Graydon Gillies).
About the author
Growing up in Calgary, Canada, I could always see the mountains sitting as a backdrop to the city. Being only a short drive away, I was lucky to spend much of my childhood exploring the Rockies, which fostered my interest in the outdoors and nature. I’ve since developed an interest in all things outdoors, including running, hiking, camping, and climbing. Since finishing my undergraduate degree, I’ve transitioned towards conducting more science in the field rather than in the lab. I’m grateful for the many opportunities fieldwork provides me to do hands-on learning in nature. As a queer biologist, I’ve grown passionate about providing these same outdoor and fieldwork experiences to marginalized students who may otherwise face barriers to participating in the outdoors. I’ve been an involved volunteer for a student-led group called QOFEI (“coffee”, the Queen’s Outdoor Field Experience Initiative), where we lend free outdoor gear to students and lead experiential learning opportunities such as backcountry camping trips for first-time campers. I’ve also been lucky to have the opportunity to mentor several undergraduate thesis students doing fieldwork with our lab, and I’ve recently had the chance to co-teach a field course in the deserts of Arizona and California. I love working as an outdoor educator and mentor, and appreciate being able to help students develop the confidence and independence that comes with learning outdoor and fieldwork skills.
The author, Graydon Gillies, in Joshua Tree National Park, California, where he was co-teaching an undergraduate field course, Desert Ecology & Evolution (Credit: Chloë Dean-Moore).
Currently, I’m finishing up my MSc degree in Biology at Queen’s University, where I’ve been studying how habitat structure and population dynamics may work in tandem to impose species’ range limits. I’ve been asking myself many questions about dispersal, population dynamics at range limits, and how the environment mediates these processes. This fall, I’ll be starting my PhD at Memorial University of Newfoundland and Labrador, where I’ll similarly be studying the processes that impose species’ range limits, but instead will be applying these concepts to understand the limitations to treeline expansion in Canada’s boreal forest.
The author, Graydon Gillies, watching the sunrise while camping along the East Coast Trail in Newfoundland, Canada (Credit: Brendan Carswell).
Like the blog post? Read the research article here.