Effects of canopy connectivity on the arboreal ant community in coffee shade trees

Abstract

Canopy connectivity influences foraging, movement, and competition in arboreal ant communities. Understanding how canopy connectivity affects arboreal ant communities could inform the development of management practices that maximize services from known biocontrol agents. We experimentally manipulated connectivity between the crowns of large shade trees to investigate the effects of canopy connectivity on arboreal ant species richness and composition in a coffee agroecosystem. A linear mixed‐effects analysis showed that the number of species observed at baits set in tree crowns increased significantly after the crowns had been connected with nylon ropes. Crowns that were connected increased in similarity of ant species composition, particularly between adjacent connected crowns. Connectivity may increase the number of species present in tree crowns by allowing ants to move and forage in the canopy while bypassing trunks with more aggressive, territorial species such as Azteca sericeasur. Because twig‐nesting species in the upper canopy have been shown to act as biocontrol agents of herbivores, an increase in species richness in tree crowns could have positive implications for agricultural pest‐control services.Abstract in Spanish is available with online material.

Naturally Occurring Vegetation Connectivity Facilitates Ant-Mediated Coffee Berry Borer Removal

“…Enhanced A. sericeasur activity on coffee plants could alter the behavior of other ant species, which could have positive or negative effects on overall pest control services due to spatial complementarity or potential negative interactions between predators [34]. However, studies find that increasing connectivity generally increases species richness [22,23,26,27], and so, vegetation connections that increase A. sericeasur mobility likely facilitate the mobility of other predatory ants in coffee systems, even by providing alternative paths to avoid aggressive altercations with A. sericeasur. Although A. sericeasur occupies only 3-5% of the shade trees at our research site [63], other ants known to contribute to CBB regulation would likely also use vegetation pathways, facilitating additional pest control.…”

“…In the absence of connectivity, trees are insular habitats with crown isolation that inhibits the movement of some taxa [26]. Connectivity in the form of lianas [24][25][26] and nylon ropes [27] shape the local community structure of arboreal ants, with higher ant species richness often occurring in trees that are connected artificially or vegetatively as compared with trees without these physical connections [26,27], and higher ant species coexistence occurring in trees with higher levels of naturally occurring canopy connectivity [22]. These results also reflect the nature of ants as highly efficient foragers, known to use branches and lianas as "opportunist walkways" that provide the quickest foraging routes by allowing for faster traveling speeds through avoiding obstacles (and hazards) on the ground [25,26], even if these routes are not necessarily the shortest distance [28].…”

“…In particular, the aggressive arboreal ant Azteca sericeasur nests in shade trees, forages on coffee shrubs, and is a keystone predator that controls the CBB [33]. Like many arboreal ants, A. sericeasur prefers walking on branches and vegetation to avoid traveling on the ground [27]. Given the role of A. sericeasur as a biological control agent, understanding how connectivity at the local scale impacts these ants has potential implications for coffee agroecosystem management.…”