Interspecific variation of plant traits associated with resistance to herbivory among four species of Ficus (Moraceae)

Background and aims To understand the defensive characteristics of interspecies varieties and their responses to herbivory damage, four species of Ficus plants (Ficus altissima, F. auriculata, F. racemosa and F. hispida) were studied. They were similar in life form, but differed in successional stages. Of these, Ficus altissima is a late successional species, F. hispida is a typical pioneer and F. auriculata and F. racemosa are intermediate successional species. We addressed the following questions: (1) What is the difference in plant traits among the four species and are these traits associated with differences in herbivory damage levels? (2) What is the difference in the damage-induced changes among the four species? Methods Herbivory damage was measured in the field on randomly planted seedlings of the four species of the same age. Defences to herbivory were also tested by feeding leaves of the four species to larvae of Asota caricae in the laboratory. A total of 14 characters such as water content, thickness, toughness, pubescence density on both sides, leaf expansion time, lifetime and the contents of total carbon (C), nitrogen (N), phosphorous (P), potassium (K), magnesium (Mg) and calcium (Ca) were measured. Leaf calcium oxalate crystal (COC) density, total Ca and N content, leaf toughness and height were measured to investigate induced responses to artificial herbivory among the four species. Key results and conclusions Herbivory damage in the four studied species varied greatly. The pioneer species, F. hispida, suffered the most severe herbivory damage, while the late successional species, F. altissima, showed the least damage. A combination of several characteristics such as high in content of N, Ca and P and low in leaf toughness, lifetime and C : N ratio were associated with increased herbivore damage. The late successional species, F. altissima, might also incorporate induced defence strategies by means of an increase in leaf COC and toughness. (C) 2004 Annals of Botany Company.