The importance of inter‐individual variation in predicting species' responses to global change drivers

• Published in: Ecology and Evolution
• Main Authors: Guscelli, E, Spicer, JI, Calosi, P
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley Open Access 2019
• Subjects: acid-base regulation; acid-base status; individual variation; ocean acidification; ocean warming; phenotypic variation; Ocean acidification
• Online Access: http://hdl.handle.net/10026.1/13848; https://doi.org/10.1002/ece3.4810

<jats:title>Abstract</jats:title><jats:p>Inter‐individual variation in phenotypic traits has long been considered as “noise” rather than meaningful phenotypic variation, with biological studies almost exclusively generating and reporting average responses for populations and species’ average responses. Here, we compare the use of an individual approach in the investigation of extracellular acid–base regulation by the purple sea urchin <jats:italic>Paracentrotus lividus </jats:italic>challenged with elevated <jats:italic>p</jats:italic>CO<jats:sub>2</jats:sub> and temperature conditions, with a more traditional approach which generates and formally compares mean values. We detected a high level of inter‐individual variation in acid–base regulation parameters both within and between treatments. Comparing individual and mean values for the first (apparent) dissociation constant of the coelomic fluid for individual sea urchins resulted in substantially different (calculated) acid–base parameters, and models with stronger statistical support. While the approach using means showed that coelomic <jats:italic>p</jats:italic>CO<jats:sub>2</jats:sub> was influenced by seawater <jats:italic>p</jats:italic>CO<jats:sub>2</jats:sub> and temperature combined, the individual approach indicated that it was in fact seawater temperature in isolation that had a significant effect on coelomic <jats:italic>p</jats:italic>CO<jats:sub>2</jats:sub>. On the other hand, coelomic [HCO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>] appeared to be primarily affected by seawater <jats:italic>p</jats:italic>CO<jats:sub>2</jats:sub>, and less by seawater temperature, irrespective of the approach adopted. As a consequence, we suggest that individual variation in physiological traits needs to be considered, and where appropriate taken into account, in global change biology ...