The world and its shades of green: a meta‐analysis on trophic cascades across temperature and precipitation gradients

Abstract

AimTo assess effects of current global temperature and precipitation gradients on the trophic function of plant-herbivore-predator interactions. Specifically, I study effects of climatic gradients on factors that control herbivore abundances: topdown, bottom-up trophic cascades and plant defences. I include predictions of climate change on shifts in trophic function, under the assumption that temperature and precipitation affect the physiology and performance of plants, herbivores and predators. Location Global.Methods A search of the relevant experiments on trophic interactions was conducted using the Web of Science and Scielo databases. Strength of trophic interactions from each experiment was studied by the calculation of the log ratio effect size (Ln R) of the control and experimental means. Each study was georeferenced and mean annual temperature (MAT) and total annual precipitation (TAP) were determined for each study location. Effect size of trophic interaction studies across the world were correlated with these environmental variables. ResultsIn total, 387 effect sizes were extracted from the literature. With the exception of bottom-up trophic cascades, trophic interactions and factors controlling herbivore abundance exhibited significant linear or quadratic relationships with either temperature or precipitation gradients: plant growth, predation and the effect of plant defence on herbivores increased with temperature. In contrast, plant growth and herbivory increased with precipitation across ecosystems. Finally, topdown trophic cascades increased towards the extremes of MAT and TAP gradients.Main conclusions This study shows climatic gradients not only affect species geographic distributions and physiological tolerance but also the strength of their trophic functionality. This is especially true for the main biotic controls of herbivore populations (i.e. predation, top-down trophic cascades and plant defences). These results suggest future climate change will cause shifts in the strength of trophic interactions, resulting in increased or reduced population control of herbivores across global ecosystems.

Biological invasions: a field synopsis, systematic review, and database of the literature

“…For example, Rodriguez-Castañeda (2012) was able to greatly increase the number of tropical ecological studies in her meta-analysis by including papers published in Spanish and Portuguese. Not only are potentially vital instances or example of invasion going unexamined that could advance the science, but serious future ecological or economic harms may be unrecognized in understudied regions where the impact of human activities is increasing.…”

The Impact of Tree Diversity on Different Aspects of Insect Herbivory along a Global Temperature Gradient - A Meta-Analysis

“…In search for factors that underlie the documented biogeographic gradient, we ask for more research on how associational effects depend on and follow global gradients in i) regional species diversity of herbivores and host plants, ii) herbivore density and pressure, especially during times of outbreaks [25, 28–30, 52–56], iii) herbivore specialization [4, 5, 8, 9, 20, 57], iv) tree defences [25, 27, 29, 31, 52, 58] and v) abiotic factors affecting tree or herbivore development (e.g. precipitation, climate stability, CO 2 -concentration, UVB-radiation).…”

“…Numerous studies also found that global gradients exist for plant species richness [21, 22], herbivore species richness [23–25], plant defences [26, 27], herbivore pressure [25, 28, 29], leaf herbivory [30] and trophic interactions [31]. Since temperature is a key driver of herbivore development and abundance [32], consumption rates [33] and host-plant choices [34] it is likely to influence these plant-herbivore interactions [33, 34].…”

Herbivore diet breadth mediates the cascading effects of carnivores in food webs

“…Although we show that the diet breadth of herbivore assemblages predicts the strength of indirect effects of plant damage for individual plant species [species-level cascades sensu (43)], we further suggest that differences in the dietary specialization of herbivores among ecosystems (18) might inform variation among ecosystems in the strength of trophic cascades (44,45). For example, some of the unexplained variation in top-down control of plant production in terrestrial vs. aquatic (5,46) and managed vs. unmanaged (46) ecosystems could be explained by the observed differences between these systems in herbivore diet breadth.…”