Does ant-plant mutualism have spillover effects on the non-partner ant community?

Mutualism benefits partner species and theory predicts these partnerships can affect the abundance, diversity, and composition of partner and non-partner species.
We used 16 years of monitoring data to determine the ant partner species of tree cholla cacti (Cylindriopuntia imbricata), which reward ants with extrafloral nectar in exchange for anti-herbivore defense. This long-term data revealed one dominant ant partner (Liometopum apiculatum) and two less common partners (Crematogaster opuntiae and Forelius pruinosus. We then used short-term characterization of the terrestrial ant community via pitfall trapping to sample partner and non-partner ant species across ten plots of varying cactus density. We found that the dominant ant partner tended a higher proportion cacti in plots of higher cactus density, and was also found at higher occurrence within the pitfall traps in higher density plots, suggesting strong positive feedbacks that promote ant partner occurrence where plant partners a...