In addition to the metabolic constraints imposed on individuals by the physiological factors in their environment, they must also be able to function within and withstand the physical forces of their external environment. Because seawater is roughly 800x denser than air, even moderate waves threaten individuals with drag forces in excess of those imposed by wind during a hurricane. Nonetheless, a remarkable diversity of marine species can be found along wave-swept shores. Bridging mechanical and ecological approaches, my research investigates the mechanical adaptations of seaweeds that allow them to persist and thrive in mechanically hostile habitats. Specifically, I focus on how tissue material properties interact with macro-morphology and growth form strategies to jointly govern mechanical adaptation in seaweeds. For instance (1) reproductive plants can compensate for the decreased flexibility associated with reproduction by altering growth form to create more streamlined shapes; (2) multi-frond plants can grow to sizes larger than would survive big waves by developing fronds with weak tissues that self-thin before storm events; and (3) kelps escape death by material fatigue common among other species and perenniate in wave-swept shores by shifting the location of their growth meristem so that the plant is always supported by new tissue.
Demes, KW, S Starko, CDG Harley. In press. Multiple stressors drive convergent evolution of performance properties in marine macrophytes. Target journal: New Phytologist. [link]
Krumhansl, K, Demes, KW, CDG Harley, & E Carrington. 2015. Divergent growth strategies between red algae and kelps influence biomechanical properties. American Journal of Botany 102(11): 1-7. [link]
Demes, KW, CDG Harley, LM Anderson, & E Carrington. 2013. Shifts in morphological and mechanical traits compensate for performance costs of reproduction in a wave-swept seaweed. Journal of Ecology 101 (4), 963-970. [link]
Demes, KW, CDG Harley, JN Pruitt, & E Carrington. 2013. Survival of the weakest: Increased frond mechanical strength in a wave-swept kelp inhibits self-pruning increasing mortality. Functional Ecology 27: 439-445. [link]
Demes, KW, E Carrington, J Gosline & P Martone. 2011. Variation in anatomical and material properties explains differences in hydrodynamic performances of foliose red macroalgae (Rhodophyta). Journal of Phycology 47(6): 1360-1367. [link]