Ground-foraging Ant Diversity and the Role of an Aggressive Ant (Azteca instabilis) in Coffee Agroecosystems

Coffee Agroecosystems;Azteca Instabilis;Natural Resources and Environment

Ennis, KatherineVandermeer, John ;

University of Michigan

关键词: Coffee Agroecosystems;    Azteca Instabilis;    Natural Resources and Environment;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/83509/KE_Submitted_Thesis.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Conventional ecological theory on competition and competitive exclusion states thatcompetition should limit diversity. However, diversity of all species is more common thancompetitive exclusion would suggest, especially in the tropics. Ants are a great study organismto ask questions of diversity and competition due to their high diversity and their relativelysessile nature of their nest. Similarly, agroecosystems offer a good habitat to study patterns ofdiversity due to the relative homogeneity of the habitat within each management regime. Westudied the patterns of alpha diversity (local species richness) of ants from two differentassemblages (coffee-foraging and ground-foraging) in the presence of a dominant and territorialant species (Azteca instabilis) in a coffee agroecosystem. We hypothesized the that alphadiversity will be the highest at intermediate distance from the A. instabilis nests because close tothe nests, the aggressive Azteca ants are successful at excluding other species, but far away formA. instabilis the normal competitive exclusion operates and reduces diversity to one or just a fewspecies. We surveyed eight sites across three management intensities (high, moderate and lowshade) for coffee-foraging ants (2 of 8 sites) and ground-foraging ants (all sites) and examinedthe species richness of each assemblage against the distance from the A. instabilis nest. Wefound no significant relationship between species richness and distance from A. instabilis for thecoffee-foraging ant species. However, there was a consistent negative trend across high andmoderate shade. This relationship was significant in five of six sites in the high and moderateshade plots. Species richness declines with increasing distance from the dominant ant (A.instabilis). In the low shade, the relationship was reversed in one site (positive trend) andnonexistent in the other. While correlative, this data suggests that competition may be shapingthe assemblage patterns found. Furthermore the interactions between A. instabilis and otherground-foraging ants may actually increase ant species richness.