Reproductive biology, ecology and conservation of Carmichaelia williamsii (Fabaceae), a vulnerable legume from New Zealand

Abstract

Carmichaelia williamsii is a threatened leguminous shrub that is most common on the Poor Knights Islands and Aldermen Islands, northern New Zealand. Flower morphology and structure of C. williamsii is suited to a bird pollination syndrome as the floral parts are stout, the petals yellow, the nectar source is distant from the stigma, and the flowers lack scent. The stigma is covered by a protective cuticle that prevents pollination until it is ruptured, which would usually be by foraging birds. Experimental self- and cross-pollinations demonstrated that if the cuticle is not ruptured fertilization will not occur, and that the species is self-compatible. Field observations on Aorangi Island, Poor Knights Islands, confirmed that C. williamsii is probably bird pollinated as plants in full flower were being systematically worked by the native passerine honeyeater the Bellbird (Anthornis me/anura; Meliphagidae). C. williamsii mainly grows in seral habitats, and populations often comprise plants of a similar height class. Introduced rats and the loss of pollinating birds could pose conservation and management problems for the species.