PHYSIOLOGICAL-RESPONSES TO ENVIRONMENTAL VARIATION IN INTERTIDAL RED ALGAE - DOES THALLUS MORPHOLOGY MATTER

Morphological variation within and among many species of algae show co rrelated life history traits. The trade-offs of Life history traits am ong different morphs are presumed to be determined by morphology. Form -function hypotheses also predict that algae of different morphologica l groups exhibit different tolerances to physiological stress, whereas algae within a morphological group respond similarly to stress. We te sted this hypothesis by comparing photosynthetic and respiratory respo nses to variation in season, light, temperature, desiccation and freez ing among the morphologically similar fronds of Chondrus crispus and M astocarpus stellatus and the alternate stage crust of M. stellatus. Ph ysiological differences between fronds of the 2 species and crusts and fronds were consistent with their patterns of distribution and abunda nce in the intertidal zone. However, there was no clear relationship b etween algal morphology and physiological response to environmental va riation. These results suggest that among macroalgae the correlation b etween Life history traits and morphology is not always causal. Rather , the link between life history traits and morphology is constrained b y the extent to which physiological characteristics codetermine these features.