Mutualism and predation have contrasting effects on pine canopy arthropod diversity

Predators are recognized to increase prey diversity by suppressing competitively dominant species, where mutualists are predicted to reduce diversity by promoting a competitively dominant partner. However this trend, and the effect of these interactions when they cooccur, remain underexplored. We investigated the effects of predation and mutualism on the diversity of pine-associated arthropods by excluding insectivorous birds and mutualist ants from branches of Pinus ponderosa and sampling arthropods during a 2-year period. We identified 92,549 arthropods to the species or morphological species level. In the absence of ants, birds had no effects on diversity while in the absence of birds, ants decreased Simpson diversity and Pieolu's evenness but did not affect species richness. However, in the presence of ants, birds increased diversity, evenness, and richness. Effects on arthropod composition mirrored diversity: birds alone had no effect on composition, ants alone increased aphid and ..., , , # Mutualism and predation have contrasting effects on pine canopy arthropod diversity

[https://doi.org/10.5061/dryad.fqz612k2z](https://doi.org/10.5061/dryad.fqz612k2z)

## Description of the data and file structure

Work was conducted at the Manitou Experimental Forest in Woodland Park, Colorado, USA (39°06′02″ N, 105°05′32″ W) in mature stands of ponderosa pines at an elevation of 2400 m. In 2001, we selected 21 sites over 750 ha area selecting four adult reproductive trees (84 trees total). In each site (“block” hereafter, \"B\" in dataset), one tree was allocated to one of four exclusion treatments: birds and ants excluded, birds alone (ants excluded), ants alone (birds excluded), and birds and ants together (Fig. 1a). Two branches per tree, ranging 0.5 to 6.0 m from the ground (2.4 ± 0.8 m, mean ± SE), were sampled for arthropods. For bird exclusions we installed a 2.5-cm opening monofilament netting bag over each branch. For ant exclusions we applied sticky paste (Tanglefoot, Grand...,