Habitat-formers support abundant and diverse communities, however, the characteristics that mediate their value to associated organisms are not always clear. Trait-based approaches can capture both inter- and intraspecific variation, potentially offering a novel way to link the characteristics of habitat-formers to ecosystem functioning. We used trait-based approaches to explore the relationship between macroalgae and their associated communities in south-eastern Australia, a region of rapidly changing ocean conditions. We documented extensive inter-and intraspecific morphological variability in macroalgae across both small- and large- scales. We found that across multiple, morphologically diverse species morphological traits were good predictors of associated communities. A manipulative experiment showed that traits affected associated community structure only in the presence of predators, suggesting that the importance of habitat-formers lies in their ability to mediate predation risk, and is not related to habitat-provisioning. Along a latitudinal gradient, algal morphological traits were found to correlate with ocean climate, highlighting the potential for future environmental change to cause significant changes to the structure of subtidal reef habitats. Such climate driven shifts in the structure of algal habitats will negatively impact associated epifaunal communities, which will cascade up food webs having implications for the functioning of these habitats.