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

Abstract

Fruit traits evolve in response to an evolutionary triad between plants, seed dispersers, and antagonists that consume fruits but do not disperse seeds. The defense trade-off hypothesis predicts that the composition of nutrients and of secondary compounds in fruit pulp is shaped by a trade-off between defense against antagonists and attraction to seed dispersers. The removal rate model of this hypothesis predicts a negative relationship between nutrients and secondary compounds, whereas the toxin-titration model predicts a positive relationship. To test these alternative models, we evaluated whether the contents of nutrients and secondary compounds can be used to predict fruit removal by mutualists and pathogens in 14 bird-dispersed plants on a subtropical island in São Paulo state, southeastern Brazil. We selected eight to ten individuals of each species and prevented fruit removal by covering four branches with a net and left fruits on four other branches available to both, vertebrate fruit consumers and pathogens. The persistence of ripe fruits was drastically different among species for bagged and open fruits, and all fruit species persisted longer when protected against seed dispersers. We found that those fruits that are quickly removed by vertebrates are nutrient-rich, but although the attack rate of pathogens is also high, these fruits have low contents of quantitative defenses such as tannins and phenols. Thus, we suggest that the fruit removal rate by seed dispersers is the primary factor selecting the levels of fruit defense. Likewise, nutrient-poor fruits have low removal of seed dispersers and low probability of attack by pathogens. These species retain ripe fruits in an intact condition for a prolonged period because they are highly defended by secondary compounds, which reduce overall attractiveness. However, this strategy might be advantageous for plants that depend on rare or unreliable dispersers.

Frugivory on Margaritaria nobilis L.f. (Euphorbiaceae): poor investment and mimetism

“…The fruit removal rate of ornithochoric fruits may reflect the amount of nutrients available to birds (Cazetta et al 2008), and varies from lipid rich fruits with high removal rate (e.g. Cabralea canjerana, Pizo 1997), to non-reward fruits with a very low removal rate (e.g.…”

Diversity of functional traits of fleshy fruits in a species-rich Atlantic rain forest

“…Fruit lipids and secondary compounds are good predictors of fruit removal (Cazetta et al 2008), what gives room for frugivores exert evolutionary pressure upon these traits, but variation across species in fruit chemistry is also determined to a large extent by common ancestry (Jordano 1995). Stiles (1993), for example, found that captive birds prefer lipid-rich fruits (but see Johnson et al 1985, Borowicz 1988, whereas mammals tend to avoid them (Debussche & Eisenmann 1989, Herrera 1989.…”

“…Fleshy fruit traits (color, morphology and chemistry) are thought to be an adaptation to their major seed dispersers or to major seed predators, such as pathogens (Herrera 1982, van der Pijl 1982, Cipollini and Levey 1997, Cazetta et al 2008. During the last decades, numerous studies on seed dispersal systems analyzed the fruit morphology and chemical characteristics, but most of these studies were species-oriented, and few took the entire community into consideration (e.g.…”

Dispersão e Caracterização de Frutos de Myrceugenia euosma em Floresta Ombrófila Mista no Sul do Brasil

“…Diversas características de frutos carnosos podem influenciar na atração e na competição por dispersores (Galetti et al, 2011), as principais são cor (Cazetta et al, 2009;Melo et al, 2011), constituintes químicos (Cazetta et al, 2008) e morfologia (Janson, 1983;Levey, 1987;Gasperin & Pizo, 2012). Espécies que produzem frutos pequenos e em grandes quantidade são classificadas na literatura como generalistas (Howe & Estabrook, 1977), atraindo uma ampla variedade de espécies de aves, muitas das quais empregam frutos em sua dieta apenas ocasionalmente (Fleming et al, 1987;Francisco & Galetti, 2002;Athiê & Dias, 2012).…”