Floral biology of the Cunoniaceae in New Caledonia and the role of insects, birds and geckos as potential pollinators

Abstract

Cunoniaceae are represented in New Caledonia by some 90 species, all of them endemic, and the family is thus a significant element in this diverse island flora. We present a descriptive survey of floral biology for the seven genera present, covering floral structure and colour, inflorescence shape, sexual system and phenology, plus details of floral visitors, where known, based on field observations; individual records of potential pollinators are tabulated in appendices. The flowers are polysymmetric (or almost so) and provide nectar and/or pollen as floral rewards. Two genera are dioecious and some species are mass flowering. Generalist entomophily is associated with several floral syndromes although the introduction of Apis mellifera has partially obscured historic relationships between some Cunoniaceae and their insect-pollinators. Codia and Pancheria both have sweetly scented, often creamish, spherical capitula and their floral visitors include honey bees, beetles, flies and native bees, especially halictids. Spiraeanthemum and Hooglandia have small, often whitish flowers in paniculate inflorescences but data on potential pollinators are few. Racemes occur in Weinmannia (flowers white, apparently scentless) and Cunonia p.p. (flowers white, pink or reddish with a faint foetid odour); visitors are mostly honey bees, plus ants, butterflies and native bees, and occasionally birds in the case of two reddish-flowered species. Ornithophily occurs in Geissois (flowers red, scentless, in bottle-brush racemes) and Cunonia macrophylla (flowers yellowgreen, in one-sided racemes); their floral visitors are commonly Meliphagidae plus some Psittacidae and Zosteropidae. Pteropodid bats are also occasional visitors to Geissois. Geckos have been reported as flower-visitors in two genera though their contribution to pollen transfer is likely to be sporadic at most. Topics that require further investigation include some details of floral biology and the floral cycle, and the possible adaptive significance of different inflorescence shapes. Unanswered questions include: What visits taxa with paniculate inflorescences?, and for all genera: Which types of floral visitor are the most efficient pollinators? For the family as a whole, generalist entomophily appears to be the ancestral mode of pollen transfer and morphological specialisations to ornithophily have occurred independently in two groups of species and possibly in a third. Our data on birds and geckos agree with a known trend for these types of floral visitation and pollination to be well developed on islands, and flower-visiting by lizards in New Caledonia is likely to be more common than has been documented so far, both in Cunoniaceae and in the flora as a whole.