Focus on: Spatial covariance of herbivorous and predatory guilds of forest canopy arthropods along a latitudinal gradient
We investigate the limitation of arthropod communities in a multi-guild analysis of forest canopies using standardized whole-forest sampling across multiple continents.
Figure description: Relationship between mean annual temperature (MAT) and the number of arthropod individuals per plot (a), per tree (b), per 1 m2 of foliage (c) and per 1 m2 of basal area (d). The colors indicate the numbers of each group of arthropods: all ants (purple), only actively moving ants (orange), caterpillars (red), mining insects (blue), and spiders (green).
Arboreal arthropods have been previously studied at the level of individual plant stems and/or limited sets of species, rather than via forest-plot censuses. However, this fine-scale understanding of plant, herbivore, and predatory arthropod distributions must be expanded, as it is a prerequisite for understanding complex food webs in forest ecosystems. We tested whether the arthropod guilds in forest ecosystems are limited by resource availability, competition, natural enemies or abiotic factors. After standardization for tree size and season, we did not find a negative correlation between abundances of different guilds within each study plot, suggesting inter-guild competition is of little importance, and top-down control of herbivores by predators is of low intensity. The strength of interactions between guilds did not change along the gradient of mean annual temperature, used as a common framework for the analysis of sites from different latitudes and altitudes. This result does not support the hypothesis of increasing intensity of biotic interactions towards tropical regions. Therefore, resources and abiotic factors appear to be more important drivers of arthropod abundances in forest canopies than competition and predation.
Mottl O., Fibich P., Klimeš P., Volf M., Tropek R., Anderson-Teixeira, K., Auga J., Blair T., Butterill P. T., Carscallen G., Gonzalez-Akre, E., Goodman A., Kaman O., Lamarre G., Libra M., Losada M.E., Manumbor, M., Miller S., Molem K., Nichols G., Plowman N., Redmond C. M., Seifert C. L., Vrána J., Weiblen G., Novotný V. (2020) Spatial covariance of herbivorous and predatory guilds of forest canopy arthropods along a latitudinal gradient. Ecology Letters. First published: 18 August 2020. DOI: https://doi.org/10.1111/ele.13579