Abstract

PELOTTO, J Pablo  and  DEL PERO DE MARTINEZ, María A. Chemical defenses in the tree Ziziphus mistol against the leaf-cutting ant Acromyrmex striatus. Ecol. austral [online]. 2002, vol.12, n.1, pp.11-18. ISSN 1667-782X.

Ziziphus mistol Griseb. (Rhamnaceae) trees are avoided by the leaf-cutting ant Acromyrmex striatus Roger (Formicidae, Attini) in a semi-arid Chaco forest of Santiago del Estero Province, Argentina. In order to find out the chemical fraction responsible of ant rejection, we analyzed putative chemical defenses (tannins, phenolics and saponins) in young and mature leaves of Ziziphus mistol and carried out field bioassays to test both polar and non-polar leaf extracts for ant-repellence. We included into our bioassays two flavonoid compounds, namely quercetin and its glycoside rutin, which are common in Ziziphus mistol leaves, and commercial quebracho tannin. Condensed tannins and total phenols were significantly in higher concentrations in mature than in young leaves. We were unable to detect hydrolyzable tannins on both young and mature leaves. Saponins were only detected in young leaves. The non-polar extract was significantly repellent, whereas the polar extract was not significantly attractive. Tannin, quercetin and rutin did not exhibit significant attractiveness or repellence at the tested concentrations. Our results suggest that some unidentified constituent(s) of the non-polar fraction of the foliar extract, likely of terpenoid nature, accounts for the rejection of the entire Ziziphus mistol leaves by Acromyrmex striatus ants.

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