The Evolution of Thallus Form and Survival Strategies in Benthic Marine Macroalgae: Field and Laboratory Tests of a Functional Form Model

Abstract

A synthetic functional form paradigm concerning hypothetically important adaptive features of algal structure and function was developed and tested by a costs/benefits strategic approach. Successional manipulations were performed by disturbing mature, environmentally constant intertidal communities; from the array of colonizing macroalgae, Ulva sp. was chosen as an opportunistic representative of pioneer seral stages, Egregia menziesii and Gelidium purpurascens/robustum as intermediate to late seral species, and Pelvetia fastigiata and Corallina officinalis as characteristic of more mature climax communities. The ranking from high to low primary producers (Ulva > Gelidium > Egregia > Pelvetia > Corallina) indicates that selection in fluctuating environments has favored opportunistic species having high net productivity, while those species able to persist in benign predictable habitats do so at the cost of lower photosynthetic rates and presumably slower growth. The kilocalories per ash-free gram dry we...