Fruit features in relation to the ecology and distribution of Acaena (Rosaceae) species in New Zealand

Fruit features of 17 Acaena species in New Zealand were investigated to det ermine the relations between reproductive allocation patterns, mode of disp ersal and species ecology. Three basic morphological types, corresponding t o major sections within the genus, are represented: spineless fruits (Sect. Pteracaena - one species), spined fruits lacking barbs (Sect. Microphyllae - 6 species), and spined fruits with barbs (Sect. Ancistrum - 10 species). The presence of terminal barbs on spines enhances fruit adhesion to animal s, and is associated with the development of longer scapes, globular many-f ruited capitula, and smaller single-seeded fruits. Barb-spined species gene rally have the broadest geographical range and habitat distribution within New Zealand, and are the only species of Acaena to occur in forests or on o ffshore islands. These species are generally strongly stoloniferous. Acaena species with barbless spines and/or no spines are often regional endemics confined to open and/or localised habitats, are rhizomatous, and may be dis persed by water, ingestion or wind. There is a tight correlation between in trageneric classification and species ecology and fruit features which requ ires testing via independent phylogenetic analysis based on molecular genet ic characters. Although avian dispersers have declined since human settleme nt, introduced mammals may be performing a similar function for barbed Acae na species.