Desiccation and thermo-tolerance of Fucus guiryi (Phaeophyceae) from its southernmost populations (Canary Islands, Eastern Atlantic)

Abstract Populations inhabiting the periphery of a species’ distribution suffer the immediate pressure of the environmental changes. Studying their physiology under stressful conditions is essential in the context of climate change. We characterized two morphotypes with measurements of length, thickness and width of the thallus of the macroalga Fucus guiryi in two localities (north and south) in Tenerife (Canary Islands), the southern limit of distribution of the species. We hypothesized that the individuals from the north locality, especially the large morphotype, would be more vulnerable to desiccation and high temperatures than those from the south. Tolerance to desiccation was tested through two long desiccation experiments and by comparing the vegetative and reproductive blades. Tolerance to high temperatures was tested by keeping the individuals in seawater (26–32 °C) for 24 h. The recovery of physiological functions after the stressful conditions was estimated through maximal photochemical efficiency of PSII. Results indicate that both of the two morphometrically differentiated morphotypes were tolerant to prolonged desiccation; however, the small one was more affected, particularly in the northern locality. The reproductive blades were hardly affected, indicating greater tolerance to desiccation than the vegetative blades. Fucus guiryi showed tolerance to high temperatures (32 °C) suggesting plasticity to future warming scenarios.