Environmental drivers of adaptive phenotypes: Do variable tidal regimes drive morphological variation in a habitat-forming seaweed?

Tasmania's surrounding coastline is affected differently by environmental parameters and results in different intertidal communities with distinctive physiological and biologica l attributes. Phenotypic variation in species can improve their fitness and facilitate adaptation to different environments. In the current study we t est ed the hypothesis that the morphology of the brown macroalga Hormosira banksii, one of the most important intertidal habitat-forming species in Tasmania, varies at multiple spatial scales that reflect important environmental stresses for H. banksii. H. banksii was sampled in 4 regions around Tasmania (lOO's of km; North, North-East, South-East and West coast), at 3 sites within each region (lO's of km) and 2 zones at each site (lO's of m; eulitoral and sublitoral). Thirty individuals were collected from each zone at each site and seven morphological variables measured. Important environmental variables were also measured for each site and correlated with the morphological data. Multivariate patterns were analysed using PERMANOVA and showed that morphology va ried across regions, sites within regions and zones and could be correlated with the tidal patterns but not wave parameters. Results suggest that environmental differences cont ribute to phenotypic variation in H. banksii but the role of genetic factors remains to be determined.