Reproductive biology ofPhormium tenax: A honeyeater-pollinated species

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Abstract
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.