International Research Fellowship Program: The Effect of Resource Availability on Mechanisms of Ant Species Diversity

Pearce Jessica M, Salt Lake City UT

Investigators

Abstract

0852917 Pearce This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four month research fellowship by Dr. Jessica M. Pearce to work with Dr. Xim S. Cerda at the Estacion Biologica de Donana in Spain. Competition is considered one of the most significant influences on community structure, especially in ant assemblages. In many communities, ant species trade-off between the ability to be good discoverers, arriving at food resources first, and to behaviourally dominate them, limiting access by other species. Although the ways in which ants dominate food are well-characterized, little is known about the patterns and mechanisms of resource discovery. This gap in the understanding of ant community structure is relatively important because recent theoretical work suggests that resource discovery, not dominance, may drive assemblage dynamics. It is suggested that fast discoverers may influence community structure by setting the rate of discovery that slow dominants must meet to persist in the community. This perspective contrasts with the traditional interpretation that discovery is used by less dominant species to ?escape? exclusion at food resources by more dominant species. Using resource supplementation and species removal experiments, three hypotheses are being tested: a) mechanisms for resource discovery by ant species vary depending on resource availability; b) the dominance-discovery trade-off is present in Mediterranean ant communities; and c) resource availability increases species richness by allowing the persistence of slow behaviorally dominant species. Resource discovery patterns and mechanisms are being characterized by performing extensive surveys of discovery (time to discovery and proportion successful discoveries) and species-specific forager density as well as by filming the patterns of search behavior of individual foragers belonging to different species. The expectation is that ant species will shift from an individual-based foraging strategy at lower resource levels to a combined group- and individual-based foraging strategy at higher resource levels. The presence and nature of a dominance-discovery trade-off is being determined by correlating the above discovery data with dominance rankings for Mediterranean species collected via behavioral trials. Given the trade-off, it is expected that a slower median time to discovery in higher resource environments occurs as a result of the appearance, persistence, and abundance of slow dominant ants. Since resource discovery is a crucial component of competition in any ant community, this mechanism-focused research is generating data that clarify how the trade-off persists and functions. These data are being used to generate models that explore how different mechanisms of resource discovery contribute to species coexistence under different levels of resource availability. Furthermore, evidence for the existence of the dominance-discovery trade-off has only been investigated in a limited number of communities. Testing for the trade-off?s presence in a new assemblage of ants serves to examine its broader importance as an explanation for species diversity. Third, this work examines the novel hypothesis that discovery, not dominance, drives ant assemblage composition. This perspective is a unique departure from past interpretation of the trade-off that has not previously been empirically examined.