Kimberly Ertel
Published: 2019
Total Pages: 47
Get eBook
Determining where species are distributed and what constrains those distributions are fundamental questions in ecology, and increasingly relevant to understanding ecological responses to climate change. Despite decades of study, however, we still lack a general understanding of the relative importance of climatic and non-climatic factors in driving species distributions. Functional traits may provide a solution, offering a way to generalize the constraints on species distributions and their responses to climate change. For example, ecologists often assume that a plant species' ability to tolerate harsh conditions, like frost, comes at the cost of competing for resources, potentially explaining where species can live across climatic gradients. To explore this topic, I conducted a greenhouse experiment using 25 plant species local to the Cascades of Washington State to test for a trade-off between two functional traits, frost tolerance and competitive ability. I also tested whether species differences in frost tolerance and relative growth rate translated to their current distributions, hypothesizing that high elevation species would be frost-tolerant but slow-growing, while low-elevation species would be sensitive to frost but fast-growing. While I found the hypothesized trade-off between frost tolerance and competitive ability across our focal species, I did not find that these traits varied by species distributions (high elevation vs. low elevation) as I had expected. Alternatively, differences in life form and family of origin explained differences among species in these two traits, suggesting that life history, long-term evolutionary processes, or both may play an unappreciated role in driving differences in these traits. In total, my results suggest that although these functional traits are related and may help explain how focal plant species respond to the direct and indirect consequences of climate change, the hypothesized stress tolerance and competitive ability trade-off may not provide us the ability to generalize those responses. Future studies could explore different metrics of cold stress tolerance and competitive ability, the physiological basis of resource allocation, consider whether trait variation is driven by relatedness, and validate these results in field studies.