Temperature dependence of competitive ability is cold-shifted compared to that of growth rate in marine phytoplankton

A new study published in Ecology Letters explores the influence temperature has on the competition and growth of different species within complex communities.

By measuring the variables of population growth rate and competitive ability (i.e. how well a species can use limited resources), the authors - including the CEM’s Dr. Joey Bernhardt - investigated the effects of climate warming on the competition amongst four species of phytoplankton under limiting nitrate. They discovered that temperature changes affect these two variables differently. As temperature increases, population growth rate also increases, but it peaks and then drops. Conversely, competitive ability decreases as temperature increases, but it bottoms out and then rises. Ultimately, competitive success appears to be highest at temperatures that are sub-optimal for growth. Not only do these findings call into question the approach of predicting species distributions based on density-independent processes such as intrinsic rates of population growth across temperature but they also provide a framework for predicting geographic ranges across temperature among species competing for a limiting resource.

Sunday, J.M., Bernhardt, J.R., Harley, C.D.G. & O’Connor, M.I. (2023) Temperature dependence of competitive ability is cold-shifted compared to that of growth rate in marine phytoplankton. Ecology Letters, 00, 1–12.