The persistence of ripe fleshy fruits in the presence and absence of frugivores

Abstract

A trade-off between antimicrobial defences and palatability to dispersers may place limits on fruit persistence in nature. The retention times of ripe fruits on 34 wild plant species under natural conditions (unbagged persistence) and when fruits had been bagged with nylon mesh to exclude frugivores (bagged persistence) were compared in Hong Kong, China (22 degrees N). Bagged persistence is a measure of the effectiveness of fruit defence while unbagged persistence is an inverse measure of attractiveness to vertebrate frugivores. Bagged fruits persisted significantly longer than unbagged fruits in 30 species, with half the species tested persisting for more than 2 months. There was a significant positive relationship between the median persistence times of bagged and unbagged fruits, suggesting that species with a high resistance to microbial infection are also less attractive to frugivores. Both bagged and unbagged fruits persisted significantly longer at lower temperatures. There was a significant positive relationship between bagged persistence time and fibre content of the fruit pulp, but no significant relationships between unbagged persistence and the six fruit traits tested (diameter, pulp as a percentage of fruit fresh weight, and lipid, total soluble carbohydrate, nitrogen and fibre as percentages of pulp dry weight). Mechanical damage significantly decreased the bagged persistence time for half of the species. Although some fruits decayed or dried up while attached to the plant, fruits of 53% of the species remained visually attractive until they fell off.

Does attraction to frugivores or defense against pathogens shape fruit pulp composition?

“…However, fruit consumption by antagonists was not measured in this study and other similar studies on limited numbers of fruit species (Cipollini and Stiles 1993;Cipollini and Levey 1997a). Even though, Tang et al (2005) also excluded seed dispersers from fruits and explained the variation in persistence time of these fruits with variation in defense against pathogens, they did not measure the amount of secondary compounds, and therefore the predictions of the models on fruit biochemistry could not be directly tested.…”

“…We excluded the second and third morphological PCs because we were particularly interested in the eVects of chemical variables based on our study questions. Moreover, previous studies reported that chemical characters are more important than morphological ones (Schaefer et al 2003;Tang et al 2005) and the Wrst morphological PC accounts for most of morphological variance allowing us to correct for fruit morphology.…”

“…We suggest that-over evolutionary timethese species improved their competitive ability by higher investment in fruit defense. This strategy might be particularly important for plant species that depend on rare or unreliable seed-dispersers (Cipollini and Stiles 1992c;Tang et al 2005). For dispersers that consume these fruits sporadically, the quantities of deterrent substances will not exceed critical levels.…”

Reproductive biology of theIlexspecies (Aquifoliaceae) in Hong Kong, China

“…There are no data on the defensive chemistry of other Hong Kong fruits, but Tang et al (2005) There have been no other local reports of seeds with undeveloped embryos in mature fruits, but I. hanceana, the only Ilex tested, was one of only eight tree species (of 40 tested) to retain viable seeds after being buried for 2 years in the forest (Zhuang and Corlett 1999).…”

“…A variety of evidence suggests that fruit chemistry reflects an adaptive balance between attracting dispersers and deterring pests and pathogens (Cipollini et al 2004;Tang et al 2005). There is also evidence that frugivores can detect small differences in fruit quality (e.g., Schaefer et al 2003a) and that ranking of fruit preferences is fairly consistent across sites and time (Herrera 1998;Carlo et al 2003).…”