Sublethal effects of a rapidly spreading native alga on a key herbivore

1. Multiple anthropogenic stressors are causing a global decline of foundation species including macrophytes often resulting in the expansion of functionally different more stressor-tolerant macrophytes. Previously subdominant species may experience further positive demographic feedbacks if they are exposed to weaker plant herbivore interactions, possibly via decreased palatability or being structurally different from the species they are replacing. However, the consequences of the spread of opportunistic macrophytes for the local distribution and life-history of herbivores is unknown.

2. The green alga, Caulerpa filiformis, previously a subdominant macrophyte on low tidal-shallow subtidal rock shores is becoming locally more abundant and has spread into warmer waters across the coast of New South Wales, Australia. 

3. In this study, we measured 1) the distribution and abundance of a key consumer, the sea urchin Heliocidaris erythrogramma, across a seascape at sites where C. filif...