Population variation in plant traits associated with ant attraction in Chamaecrista fasciculata (Fabaceae)

In different populations plants can evolve different extrafloral nectary (EFN) values to attract ants as a defense against herbivory. I quantified the intra- and inter-population variation for eight populations of Chamaecrista fasciculata to determine if variation in traits reflected herbivore selective pressures. Plants from each population were grown in a greenhouse to measure EFN size, nectar composition, sugar and volume production, and leaf pubescence throughout development. MANOVA results showed that populations varied mostly in EFN size, sugar and volume production, and less in leaf pubescence. Populations with low insect densities had small EFN and low nectar production. Positive correlations across populations between herbivore density and leaf damage on the one hand, and sugar and volume production with leaf damage on the other, suggest that differences in herbivory, resulting from the variation in ant and herbivore abundance, could have promoted differential evolution of EFN-related traits among populations.