Biological flora of New Zealand 13. Pittosporum cornifolium, tāwhiri karo, cornel-leaved pittosporum

Abstract

A comprehensive review of the morphology, anatomy, taxonomy, chemistry and ecology of the endemic New Zealand facultative shrub epiphyte Pittosporum cornifolium (Pittosporaceae) is presented. Strong habitat specificityrestricts this species to lowland forest and coastal habitats, which are widelyy et discontinuouslydistributed north of latitude 42°15'S. Pittosporum cornifolium is typically associated with old growth forest systems and low nutrient substrates, with low mean dailytemperatures in the coldest month (0.6 °C) and high mean October vapour pressure deficits (>0.5 kPa) apparentlyrestricting its distribution. Significant morphological variabilityis evident in leaves and flowers, especiallywith respect to plants from the Poor Knights Islands. Genetic analyses of five mainland populations and individuals representing Poor Knights Islands populations revealed relativelylow genetic diversity at the population level which is likelyto be the result of geographic isolation. Molecular phylogenetic studies suggest a New Caledonian origin for the species with close affinities to both P. pimeleoides subspecies. Several lines of evidence suggest recognition of the Poor Knights Islands entityas a new taxon. However, analysis of additional morphological, reproductive and molecular data across the full geographic range will be required to confirm current inferences. Although populations have declined, P. cornifolium is not currentlythreatened, however, it should be considered for reintroduction to sites in districts where its range has been severely reduced. © 2012 The Royal Society of New Zealand.