Comparison between floral and extrafloral nectar composition of Passiflora species (Passifloraceae) and their licking insects

AMELA GARCÍA, M. T., M.; FERNÁNDEZ, M. B. ; GOTTSBERGER, G.

Huerta Grande, Córdoba

Congreso; 2º Meeting of the Latinn American Association of Chemical Ecology; 2012

Asociación Latinoamericana de Ecología Química

Studies on nectar chemistry concerning floral nectar are abundant, fewer ones deal with extrafloral nectar and only very few compare floral vs. extrafloral nectar in the same taxa. Relationships between floral visitors and floral nectar concentration are well known, while relationships between floral visitors and floral nectar constituents are more rare. In contrast, relationships between extrafloral visitors (mostly ants, but also wasps, flies and other insects) and extrafloral nectar features have not been thoroughly studied. To ascertain if the chemical characteristics respond to the different visitors preferences or to phylogenetic constraints, the composition of floral nectar was compared to that of extrafloral nectar within each of three Passiflora species with both kind of these glands. Screening with HPLC for the three main sugars in nectars and 17 proteinogenic amino acids was performed in 53 samples (28 floral and 25 extrafloral) of P. caerulea, P. suberosa and P. misera. Fructose, glucose and sucrose occurred in both nectar types but their proportions varied within two species. Total amount of sugars in floral nectar was similar to that of the corresponding extrafloral nectar in all species; it was slightly lower in P. caerulea and P. suberosa. A larger range of variation of sugar total amount occurred in the extrafloral nectar of each species, while that of floral nectar was more consistent. The amino acids had a higher concentration in the floral nectars (the double or the quadruple), the number showed no clear tendency, their quality and frequency were alike in each counterpart. The chemical properties of each nectar type are discussed in relation to the plant traits associated with the interactions involved (pollination vs. antiherbivore defence) and the nutritional requirements, morphological features and behaviour of the insect partners. Evolutionary aspects of these secretory structures and of the plant taxa studied are also considered.