Biomass allocation in subantarctic island megaherbs, Pleurophyllum speciosum (Asteraceae) and Anisotome latifolia (Apiaceae)

We analysed biomass allocation of Pleurophyllum speciosum (Asteraceae) and Anisotome latifolia (Apiaceae) to explore the 'megaherb' phenomenon, the apparent importance of large-leaved, colourful forbs on southern oceanic offshore islands. The two species had similar shoot dry weights, with high leaf:stem ratios. Even within the megaherb form there are differences in shoot allocations, with Pleurophyllum investing more biomass in rhizome than foliage, compared with Anisotome. The megaherb form might be attributable to responses to the physical environment, involving the pre-emption of resources such as light, nutrients, water, or space; alternatively it may be related to the paucity of woody species at this latitude.