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We discuss studies of foliar endophytic fungi (FEF) and arbuscular mycorrhizal fungi (AMF) associated with Theobroma cacao in Panama. Direct, experimentally controlled comparisons of endophyte free (E-) and endophyte containing (E+) plant tissues in T. cacao show that foliar endophytes (FEF) that commonly occur in healthy host leaves enhance host defenses against foliar damage due to the pathogen (Phytophthora palmivora). Similarly, root inoculations with commonly occurring AMF also reduce foliar damage due to the same pathogen. These results suggest that endophytic fungi can play a potentially important mutualistic role by augmenting host defensive responses against pathogens. There are two broad classes of potential mechanisms by which endophytes could contribute to host protection: (1) inducing or increasing the expression of intrinsic host defense mechanisms and (2) providing additional sources of defense, extrinsic to those of the host (e.g., endophyte-based chemical antibiosis). The degree to which either of these mechanisms predominates holds distinct consequences for the evolutionary ecology of host-endophyte-pathogen relationships. More generally, the growing recognition that plants are composed of a mosaic of plant and fungal tissues holds a series of implications for the study of plant defense, physiology, and genetics. [ABSTRACT FROM AUTHOR]

Trade-offs among plant functional traits indicate diversity in plant strategies of growth and survival. The leaf economics spectrum (LES) reflects a trade-off between short-term carbon gain and long-term leaf persistence. A related trade-off, between foliar growth and anti-herbivore defense, occurs among plants growing in contrasting resource regimes, but it is unclear whether this trade-off is maintained within plant communities, where resource gradients are minimized. The LES and the growth-defense trade-off involve related traits, but the extent to which these trade-off dimensions are correlated is poorly understood. We assessed the relationship between leaf economic and anti-herbivore defense traits among sunlit foliage of 345 canopy trees in 83 species on Barro Colorado Island, Panama. We quantified ten traits related to resource allocation and defense, and identified patterns of trait co-variation using multivariate ordination. We tested whether traits and ordination axes were correlated with patterns of phylogenetic relatedness, juvenile demographic trade-offs, or topo-edaphic variation. Two independent axes described ~ 60% of the variation among canopy trees. Axis 1 revealed a trade-off between leaf nutritional and structural investment, consistent with the LES. Physical defense traits were largely oriented along this axis. Axis 2 revealed a trade-off between investments in phenolic defenses versus other foliar defenses, which we term the leaf defense spectrum. Phylogenetic relationships and topo-edaphic variation largely did not explain trait co-variation. Our results suggest that some trade-offs among the growth and defense traits of outer-canopy trees may be captured by the LES, while others may occur along additional resource allocation dimensions.