Influence of nests of leaf-cutting ants on plant species diversity in roads verges of northern Patagonia.
FARJI-BRENER A. & L. GHERMANDI. 2000
JOURNAL OF VEGETATION SCIENCE
Año: 2000 p. 453 - 460
Ant nests have been proposed to be the most frequent small-scale disturbances that affect vegetation patterns. However, their effects on plant diversity are little studied. We document effects of nests of the leaf-cutting ant Acromyrmex lobicornis on physical-chemical soil properties and their influence on plant diversity near road verges in a desert steppe in N-W Patagonia, Argentina. We analyzed nest soils and controls for nitrogen, phosphorus, organic matter, moisture retention capacity and texture. We also analyzed vegetation of 42 nests (30 active and 12 abandoned or dead) and 42 areas without nests. The soils around nests had a greater nutrient content and capacity to retain moisture than control soils, due mainly to the presence of organic wastes that the ants deposit on the soil surface. We found no association between nests and specific groups of plants (i.e., exclusive species), but plant diversity was higher at nest-sites than at nearby non-nest sites. This increased diversity is due mainly to a greater occurrence of native and exotic plant species on nest-sites that are uncommon in the studied area. This increased diversity is also found on nest-sites which nests are dead or abandoned. The most abundant plant species showed similar cover at nest and non-nest sites, suggesting that changes in diversity are associated more to edaphic changes caused by nests than by changes in competitive balance caused by dominant species exclusion. We propose that the nests of Acromyrmex lobicornis, through increasing the availability of resources, generate favorable microsites that can function both as refuges for less frequent native species, and as stepping stones for less frequent exotic plant species.