INVESTIGADORES
FARJI-BRENER Alejandro Gustavo
artículos
Título:
Outcomes of competitive interactions after a natural increment of resources: the assemblage of aphid-tending ants in northern Patagonia
Autor/es:
LESCANO, N.; FARJI-BRENER, AG; GIANOLI, ERNESTO
Revista:
INSECTES SOCIAUX
Editorial:
BIRKHAUSER VERLAG AG
Referencias:
Lugar: BASEL; Año: 2015
ISSN:
0020-1812
Resumen:
Ant-aphid relationships provide excellent opportunities
to study how changes in resource availability
may affect the outcome of competitive interactions. Variations
in soil fertility may affect host plant quality, with
concomitant effects on aphid abundance and the amount/
quality of aphid honeydew. This may determine the intensity
at which tending ants defend aphids against natural
enemies and competing ants. In a shrub-steppe of northern
Patagonia, aphid-infested thistles naturally grow on contrasting
fertility substrates: organic waste piles of leafcutting
ants (refuse dumps) and nutrient-poor steppe soils.
Thistles growing on refuse dumps have much larger aphid
colonies than thistles growing on steppe soils. We took
advantage of the co-occurrence in the field of plants with
contrasting aphid density to study the effect of natural
variation in food availability (aphid density) on aphidtending
ant species richness and agonistic interactions
among them. Enhanced aphid density did not promote the
coexistence of aphid-tending ant species. Although all ant
species are potential colonizers of the study plants, thistles
were often monopolized by a single ant species, regardless
of aphid density. Field experiments showed that increased
aphid density did not modify aggressiveness toward an intruder
ant, nor the probability of coexistence between two
rival ant species after the invasion of a host plant. We discuss
several hypotheses to explain why increased resource
availability does not necessarily reduce competitive interactions
in ant-aphid relationships