Sugar composition of wild fruits in Hong Kong, China

Soluble carbohydrates are the major nutritional reward in the pulp of most vertebrate-dispersed fruits (Corlett 1996, Herrera 1987, Johnson et al. 1985, Jordano 1995). However, although detailed analyses have been made of the carbohydrate content of many cultivated fruits (e.g. Nagy et al. 1990, Widdowson & McCance 1935), most studies of wild fruits have only quantified total soluble carbohydrates (e.g. Conklin & Wrangham 1994, Corlett 1996, Foster & McDiarmid 1983, Herrera 1987, Izhaki 1992). This is unfortunate because relatively minor differences in the chemical structure of nutrients can have profound implications for frugivorous animals (Martinez del Rio & Restrepo 1993), and the fruit choices of these animals may, in turn, have major implications for the abundance and distribution of plant species. Members of the sturnid-muscicapid bird lineage have been found to lack an intestinal sucrase and to avoid sucrose solutions when given a choice (Martinez del Rio et al. 1988, Martinez del Rio 1990, Martinez del Rio & Restrepo 1993, Schuler 1983). Even birds which possess a sucrase may digest sucrose relatively inefficiently and prefer hexoses in choice tests (Avery et al. 1995, Martinez del Rio et al. 1992). It has been reported that the pulp of most bird-dispersed fruits is rich in glucose and fructose but contains little sucrose, but the data set on which these generalisations were based has not been published (Martinez del Rio et al. 1992). Conversely, taste preference thresholds in primates are consistently lower for sucrose than other food sugars (Laska 1996) and both cultivated fruits, which are presumably derived largely from mammal-dispersed