Fruit characteristics and Muntiacus muntijak vaginalis (Muntjac) visits to individual plants of Choerospondias axillaris

摘要

The influence of fruit morphology and nutrient content on frugivore food selection has been discussed by several authors (McKey 1975, Snow 1981, Howe & Smallwood 1982, Janson 1983, Debussche & Isenmann 1989, Willson et al. 1989). In many studies, frugivore selection was significantly correlated with fruit characteristics such as size (Wheelwright 1985, Alcantara et al. 2000), dry pulp mass (Johnson et al. 1985), pulp to fruit ratio (Howe & Vande Kerckhove 1980, Piper 1986), fruit color (Willson & Melampy 1983, Wheelwright & Janson 1985, Willson et al. 1989), and insect infestation (Herrera 1984). Other studies have contradicted these observations (Chabot & Hicks 1982; Manasse & Howe 1983; Herrera 1985, 1987, 1995; Levey 1988). Many investigations were based on indirect statistical inference and have focused on interspecific comparisons. Comparatively few studies are available on the relationship of dispersers' selection to morphological and nutritional fruit features of individuals from a single species. Choerospondias axil/aris (Roxb.) Burtt et Hill (Anacardiaceae) is a typical pioneer tree species with a relatively large seed (17.5 X 14.3 mm). The plant depends on frugivores for seed dispersal and there are very few seedlings under the canopy of adult trees. We observed that the muntjac (Muntiacus muntijak vaginalis [Boddaert]) is the most important disperser of C. axillaris. The whole fruit is eaten; then the stone is regurgitated at a different location after several hours of rumination. The possibility of selective visits to different individuals by a frugivorous mammal may influence plant gene frequency and its evolution. The species may have evolved certain traits to enhance the attraction of frugivores to secure the dispersal of their seeds away from mother trees. This paper addresses the following questions regarding the interactions between muntjacs and morphological and nutritional aspects of fruits from a single species. First, since the muntjac is the major disperser of C. axillaris seeds, what kind of rewards do muntjacs receive from the fruits? Second, do muntjacs selectively visit individual trees and what are the factors influencing their selection?