Dispersal of Fleshy Diaspores in the Seed Floras of the South Island (New Zealand) and Tasmania

Abstract

The native seed-plant floras of South Island (New Zealand) and Tasmania are similar in size but the former is about twice as rich in species with fleshy diaspores than is the latter. In contrast, South Island has far fewer species with arillate or camnculate seeds than Tasmania. These differences in proportions may be attributed to the differential extinction of bird and ant species on the two islands during the Pleistocene Ice ages. Whereas South Island was relatively isolated at the time, Tasmania was closely connected to the Australian mainland providing refuges not available to South Island species. It is postulated that on both islands plants were less affected by glaciation than were animals. The types, sizes and colours of diaspores are similar in the floras of South Island and Tasmania, indicating that the lack of land mammals on the former island is not reflected in the dispersal biology of fleshy diaspores.