The reproductive biology and pollination of Phormium tenax was studied on Tiritiri Matangi Island and in Auckland, in the northern part of New Zealand. P. tenax reproduces asexually by offsets and sexually by large inflorescences. Offsets are monocarpic and inflorescences are terminal. Adjacent inflorescences often originate from the same genetic clone and each inflorescence usually carries many open flowers at the same time. Flower crops varied substantially from year to year.Flowers are protandrous hermaphrodites that exhibit partial dichogamy and herkogamy. The pollen or the stigma are presented sequentially for initial contact with floral visitors. Nectar rewards are greatest during the male phase of flowering.Results of controlled pollinations show that the plant preferentially outcrosses. Seeds are either large or small with the former predominating from outcrossed and natural pollinations. The capsules formed from self pollinations were rarely retained unless overall levels of pollination were reduced greatly. Where a plant was allowed to pollinate itself, a single capsule with large seeds was formed but these seeds had little endosperm.The shape and configuration of flowers ensures that large birds are the most likely pollinators. Two honeyeaters (Family Meliphagidae), the tui (Prosthemadera novaeseelandiae) and the bellbird (Anthornis melanura) were the most frequent visitors and pollinators although some introduced bird species also commonly visited, especially in Auckland City. Rather than a strict self incompatibility system, ovules respond preferentially to outcrossed pollen and nutrient resources are preferentially allocated to outcrossed zygotes. Many flowers appear to function solely as pollen donors.
New Zealand has three species of honeyeaters, all of which feed on nectar, fruit, and 'insects'. There is disagreement between published data and those becoming available from long-term studies 'On the relative proportion of these items in the diet. The effect of factors such as body size, dominance status, degree of movement, and time of year on diet and foraging behaviour are outlined, and predictions of differences between species and between sexes are made. A brief comparison of foraging in relation to the flora is made between New Zealand and Australian species.
The likely role of various pollination vectors is considered in the context of flower anatomy and the published results of past experiments. A number of insects visit flowers of both female and male vines but there is as much evidence implicating wind as there is for an insect vector. Most experiments that investigated a likely role of wind alter wind flows and are confounded by the presence of honey bees. Similarly, evidence taken as support f~r the role of honey bees is confounded by the actIOn of wind. Recent studies suggest that individual bees tend to work the flowers of one sex of vine or the other. Existing methods of measuring ~llinati~n effectiveness in kiwifruit are also quesuoned as IS our understanding of incompatibility responses. An experiment that can help resolve these problems is outlined briefly.
Feijoa sellowiana (Myrtaceae) was studied under cultivation in NewZealand, California, and Japan, to determine which floral visitors are the most effective pollinators. A large range of insects and birds visited feijoa flowers to collect pollen or feed on the sugary petals. Estimation of pollen deposited on stigmas showed that only large birds deposited sufficient compatible pollen to initiate fruit development. An exclusion experiment confirmed this. Observations of the behaviour and size of the floral visitors explained why insects and smaller birds are ineffective pollen vectors. In orchards with high densities of large birds, flowers were visited at earlier stages but, even at lower densities, visits were sufficient to ensure pollination. In orchards that lacked birds, fruit set was minimal. Bird visitation was greater at the edges of blocks and, in large blocks, fruit set was significantly lower in the centre of the block. Studies of animal movements indicated that large birds such as blackbirds (Turdus merula) and mynas (Acridotheres tristis) were the most efficient cross pollinators.
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