Biodiversity affects the structure of ecological communities, but little is known about the interactive effects of diversity across multiple trophic levels. We used a large-scale forest diversity experiment to investigate the effects of tropical tree species richness on insectivorous birds, and the subsequent indirect effect to predation rates by birds. Diverse plots (4 tree species) had higher bird abundance (61%), phylogenetic diversity (61%), and functional diversity (55%) than predicted based on single-species monocultures, which corresponded to higher attack rates on artificial caterpillars (65%). Tree diversity effects on attack rate were driven by complementarity among tree species, with increases in attack rate observed on all tree species in polycultures. Attack rates on artificial caterpillars were higher in plots with greater bird abundance and diversity, but the indirect effect of tree species richness was mediated by bird diversity, providing evidence that diversity can interact across trophic levels with consequences tied to ecosystem services and function.
UADY bird survey data
Total abundance counts from bird surveys at UADY tree diversity experiment in Yucatan, Mexico. Birds were surveyed across 32 plots containing either 1 (monoculture = M) or 4 tree species in equal proportion (polyculture = P). The tree composition within plots were from a pool of 6 species; Swietenia macrophylla (A), Ceiba pentandara (B), Cordia dodecandra (C), Piscidia piscipula (D), Tabebuia rosea (E), and Enterolobium cyclocarpum (F). Each plot was surveyed on four separate days between 0600 and 0930 amid peak bird activity, and not on rainy days. Species in table are a subset of all observed species, that include invertebrates in their diet. Taxonomic names are consistent with the Birdlife world list V3 and correspond to nodes in provided phylogeny and entries in trait table.
divfx_bird_observations.xlsx
UADY bird phylogeny
Phylogeny depicting evolutionary relationships of insectivorous birds (44 species) observed at UADY tree diversity experiment. Phylogeny is a 95% CI consensus tree derived from 200 trees (accessed at birdtree.org). Branch lengths are calculated as the mean edge length using the "phytools" package in R. This phylogeny is used to calculate PD of foraging birds.
divfx_bird_phylogeny.tre
divfx_caterpillar_predation
These data are from a field experiment at the UADY tree diversity experiment in which clay caterpillars were applied to trees to assess predation rates. Predators were identified from bite marks on the clay models as either bird, arthropod, or mammal. Clay caterpillars were exposed to predators for 2 consecutive days in an experiment that occurred twice in July 2015. Caterpillars were assessed for bite marks every 24 hours. Each row of this dataset informs the fate of each individual caterpillar after each 24 hour exposure period. Predator attacks are quantified as absence/presence for each 24-hour period. Data are given on the identity of tree species in which they were placed and whether the surrounding experimental plot was a monoculture (M, 1 tree species) or polyculture (P, 4 tree species).
