Gender dimorphism in indigenous New Zealand seed plants

The frequent occurrence of gender dimorphism has long been recognised as one of the distinctive features of the New Zealand flora. We list 83 seed plant genera in which gender dimorphism occurs, and document habit, pollination, and dispersal characters for each genus. This means that gender dimorphism is represented in 23% of the genera in the flora; however, not all of these genera are uniformly dimorphic in gender—40% of them include some species or populations that lack gender dimorphism. We estimate that gender dimorphism has arisen autochthonously in 17 of the 83 genera— therefore, gender dimorphism evolved elsewhere in most cases (80%), and was established in New Zealand by subsequent migration. A comparison of the genera in which gender dimorphism occurs with the remainder of the flora shows that gender dimorphism is strongly correlated with fleshy fruits, and with woody habits. No correlation was found between gender dimorphism and pollination mode, perhaps because relatively unspecialised pollination systems are another characteristic feature of the New Zealan flora. Among genera for which gender dimorphism appears to have arisen autochthonously, a liane habit seems to have been a contributing factor, whereas fleshy fruit and pollination mode were not.