Anti-herbivore defense trade-offs : a comparison of Passiflora capsularis, Passiflora helleri, and Passiflora sexflora (Passifloraceae)

Plants in the Tropics must evolve strategies for combating high levels of herbivory with few available nutrients. This results in possible tradeoffs between chemical and structural defenses. Three species of tropical passion vines, Passiflora capsularis, Passiflora helleri, and Passiflora sexflora (Passifloraceae) were examined for possible tradeoffs in cyanide, leaf toughness, glands and pubescence as anti-herbivore defenses. One young and one old leaf were collected from ten individuals of each species and analyzed for cyanide concentration and leaf toughness. In addition, observations were made regarding habitat, pubescence and presence or absence of blade glands. From the results it is clear that each species analyzed has adapted different anti-herbivore defense strategies. Passiflora helleri (mean = 119.88 µg/g leaf, Std Err. ± 39.54) demonstrated markedly higher concentrations of cyanide production as well as blade gland than P. capsularis (mean = 24.04 µg/g leaf, Std Err. ± 18.15) and P. sexflora (mean = 0.05 µg/g leaf, Std Err. ± 0.006), which did not have blade glands (N = 59, t = 2.01, P = 0.05). Passiflora sexflora showed observably more pubescence than either of the other two species. And P. capsularis exhibited an observable tradeoff in the levels of cyanide produced in young versus old leaves (N = 8, F = 5.14, P = 0.04, DF = 1). All species were found in the understory along well cleared trails. These data suggest that the anti-herbivore defense strategies employed by Passiflora spp. are diverse and represent evolutionary tradeoffs between different defenses under similar selective pressures. Las plantas en los trópicos deben evolucionar estrategias para combatir los altos niveles de herbivoría con los pocos recursos disponibles. Esto puede resultar en compensación diferencial entre las defensas químicas y estructurales. Se examinaron tres especies de bejucos, Passiflora capsularis, Passiflora helleri, y Passiflora sexflora, para evaluar la posibilidad de compensación entre el cianuro, la dureza de las hojas, las glándulas y pubescencia como defensas anti-herbivoría.https://digitalcommons.usf.edu/tropical_ecology/1015/thumbnail.jp