Divergent Defensive Strategies of Young Leaves in Two Species of Inga

Abstract

Abstract. In the recently radiated genus Inga (Fabaceae), few nucleotide substitutions have accumulated among species, yet large divergences have occurred in defensive phenotypes, suggesting strong selection by herbivores. We compared herbivory and defenses of young leaves for I. goldmanii, a more derived species that follows a ''defense'' strategy, and I. umbellifera, a more basal species that follows an ''escape'' strategy. The two species suffered similar rates of herbivory (22% of the leaf area eaten during expansion) but were attacked by different communities of herbivores. I. goldmanii relied heavily on extra-floral nectaries and on a diversity of effective secondary metabolites, while I. umbellifera minimized damage through rapid leaf expansion and synchronous flushing. The major classes of secondary compounds in both species were flavanoids and non-protein amino acids; however, there were large differences in structure, biosynthetic pathways, and efficacy against herbivores. Growth rates of lepidopteran larvae were significantly lower when fed artificial diets with crude extracts from I. goldmanii as compared to I. umbellifera. Flavanoids accounted for the majority of growth reduction in both species. I. umbellifera had more unusual flavanoids and a non-protein amino acid not reported from plants, but the more common flavanoids found in I. goldmanii were more bioactive against herbivores. I. goldmanii also had greater ant visitation to extrafloral nectaries, suggesting that there was no trade-off between biotic and chemical defenses. In contrast, young leaves of I. umbellifera expanded more rapidly, minimizing the window of vulnerability before toughening. Resources for rapid expansion may have been reallocated from chloroplast development as I. umbellifera delayed the greening process until after full leaf expansion. Leaves were also produced synchronously, which can satiate herbivores and reduce damage. These defense differences are reflected in almost completely nonoverlapping herbivore faunas and the more frequent occurrence of generalists on I. umbellifera. To understand why defenses have evolved, it is important to view them in light of the herbivore community as well as in the context of the other co-occurring traits. We hypothesize that the effectiveness of chemical defenses determines whether a species follows the evolutionary path of ''defense'' or ''escape'' strategies.

The evolution of antiherbivore defenses and their contribution to species coexistence in the tropical tree genusInga

“…An Inga-specific fractionation protocol (Fig. S5) developed in the lab at the University of Utah produced seven chemically distinct (19,47) fractions: lipids, phenolics, saponins, amino acids, organic acids, proteins, and the insoluble parts of the cell walls (marc). Two of these, phenolics and saponins, either have been shown to account for the great majority of the deterrent activity in Inga extracts (19,47) or are presumed to be deterrent based on their mass abundance and the literature (27).…”

Seasonal Variation of the Chemical Composition and Antimicrobial and Cytotoxic Activities of the Essential Oils from Inga laurina (Sw.) Willd.

“…Other terpenoids found in relevant concentrations were linalool (2, 5.17%), α-terpineol (3, 4.18%), geraniol (4, 3.71%) and γ-eudesmol (5, 3.48%) (Figure 1). In addition to terpenoids, the major compounds identified in this essential oil were hexadecanol (6, 8.34%), heptadec-8-ene (7, 7.66%), homosalate (8,4.60%), hexadecane (9, 4.57%) and phytone (10, 3.90%) (Figure 1 In the leaves' essential oil, a total of 22 compounds were identified for the same season ( Table 1). Most of the compounds identified were esters, representing 42.35% of the total, while the bark's essential oil accounted for 10.88% ( Table 2).…”

“…Several species of Inga are used in folk medicine as an anti-inflammatory, an antidiarrheal and a nasal decongestant, and for skin treatment, earache and cleaning teeth [1,2]. Studies of these species have reported the isolation of some metabolites such as depsides [3], metabolites of nitrogen [4], pipecolic acids [5,6], steroidal glycosides [7] and phenolic compounds [1,[7][8][9][10][11]. However, there are few chemical studies available related to I. laurina species [12].…”

Using DNA to assess errors in tropical tree identifications: How often are ecologists wrong and when does it matter?

“…G. Dexter, unpublished data) and used the following primers for amplification: ITS 4 (White et al 1990) and ITS 5a (Stanford et al 2000). We selected the trnD-trnT region because it contained the highest number of polymorphic sites among multiple chloroplast intergenic regions that were initially screened in the genus (Coley et al 2005; R. T. Pennington, unpublished data). We amplified the trnD-T region using the following primers: trnH (trnT in Demesure et al 1995) and trng2 (Oh and Potter 2003).…”