Background/Question/Methods Plants defend themselves from herbivores using a variety of defenses ranging from physical and chemical defenses to recruiting mutualistic defenders. Irrespective of the type of defense, plants need to allocate resources for defense production resulting in less resources for growth and reproduction, and this allocation pattern may also change with resource availability. Past research has shown that allocation to defense decreases with increasing resources, especially for between species comparison. Additionally, research has also shown that plant functional traits that determine plant growth and function are strongly affected by resource availability. Although evolved for different purposes, it is likely that traits from defense strategies and leaf economic spectrum strategies may interact synergistically or antagonistically within a plant to determine groups of traits that would optimize plant fitness. Recent attempts at integrating the two axes of trait variation have explored interspecific trends informing us of potential evolutionary trade-offs. To test for resource induced trait trade-offs, we studied intraspecific variation in defense and LES traits in a widely distributed shrub, Solanum incanum, exposed to natural mammalian herbivory. We sampled at 43 sites across the Serengeti National Park along natural gradients of rainfall, soil N and P availability. At each site, we sampled five individuals for a range of defense and LES traits including thorn density, phenolic content, lignin and cellulose content, specific leaf area and leaf nutrient content. We specifically asked 1) Are the defense and LES traits linked within species? 2) How does resource availability affect traits or groups of traits? Results/Conclusions Preliminary results from a PCA suggest that upto 70% of the variation in the study was accounted for by the first two principal component axes, one of which was along the leaf economic spectrum with increasing SLA and decreasing Narea and the other along leaf structural to non-structural content. Variation in thorn density, a physical defense trait was unrelated to any of the LES or chemical defense traits and mostly loaded along the third PCA axis. Surprisingly, variation in LES- and thorn density- associated PC axis were both associated with soil P but not with rainfall or soil N which have been shown to be important resources driving plant defenses in other ecosystems. Thus, our work provides the first example for integration of LES and defense traits within species and also highlights a potential role for phosphorus in driving plant-herbivore interactions in terrestrial systems.
