LESCANO Maria natalia
congresos y reuniones científicas
Trophic cascade effect: leaf-cutting ant nests, plants, aphids and tending ants
LESCANO, MN; FARJI-BRENER, A.G.
Congreso; VI Southern Connection Congress; 2010
In a trophic chain, bottom-up effects can be affected by the presence of small-scale soil disturbances enhancing resource availability. An increase in the quantity or quality of resources at basal levels would allow more energy flow through the trophic chain. If the individuals in the upper levels are efficient in resource exploitation, their population size and species richness may increase. In Patagonian desert steppe, we evaluated how the high nutrient availability generated by the leaf-cutting ant Acromyrmex lobicornis refuse dumps (RD) affects ants-aphids-thistle interactions. We selected plants of Onopordon acanthium growing in RD and non-nest soils (NNS). In each plant we measured nitrogen content (N), height, number of leaves and inflorescences, aphid density, and abundance and number of attending ant species. Plants in RD had higher foliar N and were larger than those in NNS. Aphid density and ant abundance attending them were higher in plants growing in RD. This suggests that the increase in the quality of O. acanthium as a result of growing in RD improves aphid abundance, and larger aphid populations may sustain more ant individuals. Our results suggest that the higher soil fertility generated by leaf-cutting ant nests can affect plant size and quality, and in turn, aphid abundance and their tending ant assemblage. Thus, the small-scale soil disturbances can spread through the trophic chain. Project sponsored by FONCyT, PICT # 25314.