Flower biology in New Zealand

Abstract

Research on flower biology began in New Zealand in the early 1870s under the influence of Darwin's work on orchids, but from the turn of the century there was a decline in interest until the 1950s. Spring and summer are the main flowering periods, but many species flower in winter and examples are described. Of some 1800 indigenous species of flowering plants 12–13% are dioecious, c. 2% gynodioecious, and 9% monoecious. But in many cases the unisexuality is characteristic of a widespread family or genus and cannot be claimed as having evolved in New Zealand. The morphological differentiation between male and female flowers settles down at a level characteristic of the genus and the degree of differentiation need not reflect the time since differentiation began. In hermaphrodite species heterostyly is not known, and demonstrated examples of self-sterility are few. A classification of 649 species with attractive flowers gives 60.6% white, 17.2% yellow, 12.4% blue lilac or dark purple, 5.7% red to crimson, and 4% green. A large sample from the British Isles has 25.1% white flowers. It is emphasised the flowers classified as white are rarely completely so, that a white plus yellow group is important, and that not all the flower colours need have evolved under New Zealand conditions. Nectar and honey-dew from native plants provide useful honey sources, but work on nectar has been confined to cases of bee poisoning. Available pollinators are birds (7 spp.), bats (1 sp.), butterflies (16 spp.), and solitary bees (c. 40 spp.) as well as many species of moths, beetles, and flies and several introduced bees. The general impression is of widespread self-fertility in hermaphrodite plants and variety in respect of insect visitors. It is emphasised that although much attention, everywhere, has been given to methods of pollination, more attention should be given to the results, i.e., the percentage of ovules which produce seeds. And it is also emphasised that a better understanding of the characteristics of New Zealand flowers will be obtained by studying their relatives in other lands.