Effect of harvester ants of the genus Pogonomyrmex on the soil seed bank around their nests in the central Monte desert, Argentina

PIRK, G. I.; LOPEZ DE CASENAVE, J.

ECOLOGICAL ENTOMOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 vol. 29 p. 610 - 619

0307-6946

The abundance and composition of soil seed banks is a key determinant of plant community structure. Harvester ants can remove huge quantities of preferred seeds close to the nest affecting composition and spatial distribution of plants. In the central Monte desert (Argentina) ants of the genus Pogonomyrmexhave high seed removal rates, especially of five main grasses. The aim of this study was to establish if their foraging activity affects spatial patterns of the soil seed bank around their nests. Our hypotheses were: (1) removal by ants decreases seed abundance of preferred species in the soil; (2) the effect varies in time. Soil seed abundance was assessed at different distances from Pogonomyrmex nests in the litter and in bare soil at the beginning, the middle and the end of the season (late spring-early autumn). A lower seed abundance of preferred species was observed close to the nest in the litter at the end of the season. Non-preferred species showed no distance gradient. The lower foraging activity and seed consumption at the beginning of the season could explain the temporal variation of the spatial effect. This was only observed in the litter, probably because of the higher removal frequency in this substrate. Colonies of Pogonomyrmex spp. could enhance the heterogeneity of soil seed banks in the central Monte desert from summer to beginning of autumn. Implications for vegetation dynamics depend on the degree to which seed density limits perennial grasses recruitment after ant activity season.