Taxonomic and ecological studies of Bornean Nepenthes
This study shows that Nepenthaceae is represented by 81 species. These species exhibit odd patterns of distribution which may be correlated to the past geological events, relative youth of the group, and the pre-existence of the species on the isolated island on the east during the continental drift. The ecology of 33 Bornean Nepenthes is described. They grow from sea-level to ca. 3500 m. They prefer to grow in exposed habitat but scarce or absent in closed canopy forest and on bare ground; they also show preference for or are restricted to particular habitats. This study also shows that vegetative and reproductive characters are variable between and within the species; some characters are found to be of diagnostic value in a particular species and useful in the recognition of the hybrids. Pitcher morphology, glands, and trichomes show more or less similar variation. Pollen morphology shows no variation but tetrad sizes are variable but generally overlapping between species. Leaf flavonoids profile shows interspecific and intraspecific variation, and is useful in the recognition of the hybrids. 34 species and 3 natural hybrids of Bornean Nepenthes have been described. A dichotomous key to identify the species has been constructed. 16 new taxa have been recognised viz: 4 species, 1 subspecies, 3 hybrids, and 8 varieties. The population study of 10 species shows scattered and clustered distribution. The distribution is influenced by soil, topography vegetation type, and light intensity. Seedling and juvenile plants are more abundant than mature plants. Fertile plants are relatively few, and with more male than female plants. Studies on reproductive biology shows reproductive syndromes suggesting insect pollination. A pollen-trapping experiment in N. villosa showed that wind plays no part in pollination. PCA of insect visitors shows the correlation with altitude. Diptera is common at high altitude, whereas Hymenoptera and Formicidae are common at low altitude. Bornean Nepenthes studied display a carnivorous syndrome. The pitcher of the 18 species studied attracted at least 18 faunal groups. This study also shows that lower pitchers trap more creeping fauna, and upper pitchers attract more flying insects; the differences in prey compositions between species is correlated with habitat; Formicidae are most abundant in pitchers of lowland species; species of high elevation attract a broad spectrum of prey. The liquid-filled pitcher provides a food source for animals, and the continuous production of new pitchers provides an ideal breeding ground for insects like Culicidae, Chironomidae, Phoridae, and Calliphoridae.