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Evolutionary ecology of seaweed strength and flexibility

University of British Columbia

An organism’s success is largely dependent upon its ability to function and survive within the physical constraints of its environment. The wave-swept shoreline is one of the most mechanically challenging environments on Earth, with passing waves imposing hydrodynamic forces comparable to those in a hurricane every 5-10 seconds. Nonetheless, the wave-swept intertidal hosts an exquisite diversity of plants and animals. I used field and laboratory techniques to examine morphological and material adaptations of seaweeds to life in high-energy environments. In Chapter 2, I experimentally manipulated size and shape of 16 species of foliose red algae and showed that variation in tissue material and structural properties explain differences in hydrodynamic performance among species- thinner, more flexible tissues allow blades to reconfigure in flow and reduce drag. Because material and structural properties may shift through an organism’s lifespan, I then investigated how reproduction and aging impact seaweed mechanical traits. In Chapter 3, I documented the mechanical costs associated with reproduction in the winged kelp, Alaria marginata, and found that shifts in other structural and material traits compensated for the increased drag associated with reproductive blades. In Chapter 4, a survey of 27 species of foliose algae showed that aging affected material properties of all species similarly. However, the implications of aging tissues on mechanical design varied with the growth form of the species: apically growing red algae have their oldest (stiffest) tissue attaching their blades to the substrate, while kelps, whose blades grow basally, are supported by their newest (most flexible) tissue. Finally, in Chapter 5, I tested for intraspecific variation in mechanical traits and found that variation among individuals (Egregia menziesii) at an exposed site accurately predicted survivorship during winter storms. Individuals with weaker fronds were more likely to survive because their increased propensity to self-prune in smaller waves reduces their risk of dislodgement in larger waves. Taken together these results support the notion that the material and structural properties of organisms have important functional consequences and highlight how mechanical traits can impact ecological and evolutionary processes.

Text

2013-04-20

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/44342

Zoology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/