Patterns of nectar secretion in five Nepenthes species from Brunei Darussalam, Northwest Borneo, and implications for ant-plant relationships

The distribution of nectaries and the temporal and spatial pattern of necta r secretion are compared for five Bornean lowland species of Nepenthes (N. albomarginata, N, bicalcarata, N. gracilis, N. mirabilis var. echinostoma, N. rafflesiana) based on results from field studies conducted in Brunei Dar ussalam, Northwest Borneo. Leaf development together with temporal and spat ial pattern of nectar secretion is also given for cultivated Nepenthes bica lcarata, a myrmecophytic species that, in terms of nectar production, appea rs to be exceptional within the genus. The number of ants trapped in frequently visited pitchers of N. bicalcarata and N, mirabilis var. echinostoma was counted over a set period. The perce ntage of trapped individuals was remarkably small. It ranged from 0.75 to 1 .59% of present ants in N. bicalcarata and from 0.34 to 0.42% in N. mirabil is. The function of extrafloral nectaries in Nepenthes with special reference t o N. bicalcarata as well as implications for ant-plant relationships are di scussed.