Showing papers on "Ant colony published in 1994"

Scale effects of vegetation on forager movement and seed harvesting by ants

Abstract: The responses of animals to patch structure at different spatial scales influence how processes such as foraging and species interactions vary with spatial scale or translate across levels of organization. We investigated how seed harvesting by the western harvester ant (Pogonomyrmex occidentalis) was affected by vegetation structure in a shortgrass steppe ecosystem at levels of organization ranging from individual ants to populations and at spatial scales from 0.1 m 2 to 15 ha. In the first of two experiments, we used a hierarchical experimental design to assess the magnitude and variation in seed harvesting (1) among ant colonies in three pastures differing in livestock grazing intensity, (2) among colonies within pastures, and (3) among plant cover types within colonies

Social Resilience in Individual Worker Ants and Its Role in Division of Labour

Abstract: This paper extends the notion of spatial efficiency in the organization of social insect colonies. We demonstrate for the first time that ants (individually marked workers in three colonies of Leptothorax unifasciatus (Latr.)) are not only faithful to particular positions within the nest, but they also quickly readopt these positions, relative to one another, when the colony emigrates to an entirely new nest site. This phenomenon, which we term social resilience, has implications for the role of learning in the maintenance of an efficient division of labour to which, in part, the great ecological success of social insects has been attributed. As we demonstrate with observations of another three colonies over a period of six months, workers change their positions asynchronously and different age cohorts are intermingled. Thus the reconstruction of colony spatial order cannot be accounted for by age-based task allocation (i.e. age polyethism), as at any one time the colony meshwork represents a heterogeneous mixture of different generations. These findings also show that ant colonies have a much more precise spatial structure and greater cohesion than previously assumed, and demonstrates the importance of detailed quantitative examination of the sociogenesis or developmental biology of these societies.

The unusual social organization of the antPachycondyla tridentata (Formicidae, ponerinae)

Abstract: Colonies of the ponerine antPachycondyla tridentata from Malaysia occur with and without queens. In a total of 7 colonies we found more than 80% of the workers to be mated, irrespective of the presence or absence of queens. This is a hitherto unknown social organisation in ants. Queens and workers competed equally for reproduction. In the colonies investigated several ants were laying eggs. Behavioral observations revealed persistent dominance interactions between colony members. A few ants, but not necessarily a queen, occupied top positions. Removal of the most dominant ants led to a new hierarchy in which subordinate ants with developed ovaries were attacked significantly more frequently than non-reproductive ants. On the average, callows were more aggressive than older subordinate ants, displacing most of the older laying workers in one colony. Nestmate recognition tests revealed that non-reproductive ants were much more aggressive towards foreign ants than were ants with developed ovaries.

Dispersal of Miconia cabucu seeds by ant Trachymyrmex spp.

Abstract: The influence of ants (Trachymyrmex) on Miconia cabucu seed dispersal is reported. M cabucu is a common tree of secondary forest in South Brazil tropical rain forest. The ants eat the sweet, juicy pericarp of M. cabucu, gathering fruit fragments with seeds attached. The seeds dropped or lost along the way may germinate and establish plants at a new site. The seeds that were carried back to the ant nest may benefit from being placed in these ant colonies, because the photoblastic seeds show an increased vigor after remaining in dark conditions for some time.