Aspects of Pitcher Morphology and Spectral Characteristics of Six BorneanNepenthesPitcher Plant Species: Implications for Prey Capture

Pitcher plants of the genusNepenthesattract and trap invertebrateprey using nectar-secreting pitchers. Pitcher morphology andspectral reflectance characteristics were investigated for sixNepenthesspeciesfrom northwest Borneo (N. albomarginata, N. ampullaria, N. bicalcarata,N. gracilis, N. mirabilisvar.echinostomaandN. rafflesiana).Morphological measurements focused on the size of the pitcherrim (or peristome, the site of the major nectaries) in relationto pitcher length. The results show considerable interspecificvariation in morphology. Spectral reflectance measurements quantifiedthe degree of colour contrast between the peristome and pitcherbody, from ultraviolet (UV) to red wavelengths. The contrastmaxima for each species were compared with insect visual sensitivitymaxima. The six species showed a wide range of reflectance patterns,with pitchers ofN. rafflesianapossessing the greatest degreeof ‘fit’ between contrast maxima and insect sensitivitymaxima, in the UV, blue and green regions of the spectrum. Basedon the morphological and reflectance analyses, we hypothesizedthat pitchers ofN. rafflesianawould be more attractive to anthophilous(flower-visiting) invertebrates than the sympatricN. gracilis.Analysis of prey contents generally supported the hypothesis,suggesting possible interspecific resource partitioning. Morphologicaland spectral characteristics of the other species are discussedin relation to published studies on prey capture by those species.Copyright1999 Annals of Botany Company Borneo, carnivory, colour,Nepenthesspp., pitcher plants, prey attraction.