Effects of Canopy Connectivity on Ant Community Assembly on a Shaded, Oraganic Coffee Farm

vegetation structure;arboreal ants;canopy connectivity;arboreal ants;School for Environment and Sustainability

MacDougal, FernBurnham, Robyn ;

University of Michigan

关键词: vegetation structure;    arboreal ants;    canopy connectivity;    arboreal ants;    School for Environment and Sustainability;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/150643/MacDougal_fern_Thesis.pdf?sequence=1&isAllowed=y

瑞士|英语

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

【 摘 要 】

Canopy connectivity influences foraging, dispersal, and competition in arboreal antspecies, with implications for ant community assembly. Connectivity among the crowns of shadetrees varies greatly with agricultural intensification in agroforestry systems, where some antspecies have been shown to act as biological control agents against agricultural pests.Understanding how canopy connectivity affects arboreal ant communities could aid in thedevelopment of management practices that maximize biological control services from arborealant species. I used a manipulation of connectivity between the crowns of large shade trees toinvestigate the effects of canopy connectivity on arboreal ant species richness, composition, andco-occurrence rates in a coffee agroecosystem. Further, I examined the effects of the majordominant arboreal ant species, Azteca sericeasur, on ant species density and composition ontrunks and crowns of upper shade trees.A linear mixed-effects analysis showed that the number of species observed at baits set intree crowns increased significantly after the crowns had been connected with nylon ropes (p =0.028). In trees occupied by A. sericeasur , lower numbers of species were observed at baits evenin the crown (p = 0.067). Crowns that were connected increased in similarity of ant speciescomposition, particularly between adjacent connected crowns. Composition also significantlydiffered between both trunks (P = 0.003) and crowns (P = 0.014) that contained A. sericeasurnests and those that did not. Overall C-scores combined with an analysis of co-occurrence ratesof individual pairs of species indicate that this arboreal ant community is not characterized byhigh rates of segregation, and pairwise competitive interactions are not among the mostimportant forces structuring community assembly here.In timed observations of connecting lines between tree crowns, only arboreal-nesting antspecies were recorded, reinforcing the idea that canopy connections are most significant tostrictly arboreal species. Connectivity may increase the number of species present in tree crownsby allowing ants to disperse and forage in the canopy while bypassing trunks with moreaggressive, territorial species. While the keystone ant A. sericeasur makes heavy use ofconnections within lower vegetative strata, I found that other species, such as twig-nestingspecies, are more likely to make use of connections in the canopy above 11 m. Because sometwig-nesting species in the upper crown have been shown to act as biological control agents, anincrease in species density in tree crowns could have positive implications for agricultural pestcontrol services.