Graydon J. Gillies, Amy L. Angert, Takuji Usui
This is a plain language summary of a Functional Ecology research article which can be found here.
To persist, species must confront competitors that require the same resources. When two competitors are growing in an environment where a certain resource is scarce, the competitor that is able to maintain a growing population with less of that limiting resource (quantified by the population with a lower “R*” for that resource) will outcompete the other. However, what is unclear is how these resource requirements of competitors (i.e., their R* values) change when exposed to stressful conditions. Do species that live in high-stress environments require more resources for maintenance and survival, limiting the resources they can allocate to competition? Would these physiological changes consequently affect the species’ competitive ability?
Using common duckweed, a small aquatic plant, we conducted an experiment to test whether populations require more resources to grow (i.e., require a higher R*) when exposed to heat stress. We also tested whether these nutrient requirements change across common duckweed collected from different bodies of water across the Pacific Northwest to understand if populations from different evolutionary lineages, or ‘genotypes’, have varying resource requirements. Lastly, we also tested if these different genotypes have to strategically opt for being good at growing at either low nutrients or high nutrients, and whether these patterns changed when grown in high temperatures. We found that, indeed, common duckweed populations require a greater amount of nitrogen —an essential resource— to maintain population growth under stressful temperatures. Furthermore, different duckweed genotypes showed variation in the amount of resources required, but this variation was lower when grown in stressful conditions. Lastly, we found that our duckweed genotypes don’t have to choose whether to be better at growing at low or high nutrient concentrations, and instead found that the genotypes that are best at growing with low nutrients are also best at growing with high nutrients. Our results are important for better understanding how species interactions, in particular competition, may change in response to anthropogenic impacts and global warming.
Functional Ecology: Plain Language Summaries 