Demography and Spatial Extent of Atta cephalotes Colonies

Undergraduate #76
Discipline: Biological Sciences
Subcategory: Ecology

Anna DiPaola - University of California, San Diego

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Atta cephalotes is a dominant herbivore and ecologically important ecosystem engineer in the neotropics. Despite extensive studies of the leaf cutter ant’s symbiotic relationship with fungus, we know little about their demography and spatial footprint. I resurveyed nests from a 2012 study to estimate the rates of Atta cephalotes colony inception and survivorship in two soil types at the La Selva Biological Research Station in Costa Rica. I investigated the relationship between foraging trail length and three proxies for colony size: number of nest entrances and vents, nest surface area, and daily vegetation intake in 12 colonies in primary and secondary forest. A. cephalotes colonies at La Selva appeared to be growing at a rate of 1.3 nests every three years and increasing in spatial density along paved trails, with slightly higher density in alluvial soils than in residual (volcanic) soils. Larger nests with more entrances and vents took in more vegetation per day. The sum of a nest’s foraging trails had a marginally significant positive relationship with daily vegetation intake. Nests in primary forest were larger on average than those in secondary forest, but this difference was only marginally significant; I found no significant difference in vegetation intake and foraging trail length between primary and secondary forest. As further studies reveal how Atta cephalotes affects soil properties and vegetation, estimating their colony demographic parameters and spatial influence informs the extent to which leaf cutter ants’ effects on ecosystem processes scale up over time and space.

Funder Acknowledgement(s): The National Science Foundation, Research Experience for Undergraduates

Faculty Advisor: Jane Zelikova,