Opposite latitudinal patterns for bird and arthropod predation revealed in experiments with differently colored artificial prey

Abstract

The strength of biotic interactions is generally thought to increase toward the equator, but support for this hypothesis is contradictory. We explored whether predator attacks on artificial prey of eight different colors vary among climates and whether this variation affects the detection of latitudinal patterns in predation. Bird attack rates negatively correlated with model luminance in cold and temperate environments, but not in tropical environments. Bird predation on black and on white (extremes in luminance) models demonstrated different latitudinal patterns, presumably due to differences in prey conspicuousness between habitats with different light regimes. When attacks on models of all colors were combined, arthropod predation decreased, whereas bird predation increased with increasing latitude. We conclude that selection for prey coloration may vary geographically and according to predator identity, and that the importance of different predators may show contrasting patterns, thus weakening the overall latitudinal trend in top‐down control of herbivorous insects.

Search for top-down and bottom-up drivers of latitudinal trends in insect herbivory in oak trees in Europe

“…We found no evidence that latitude or climate influenced leaf-chewing herbivores, but we found that climatic factors rather than latitude per se were the best predictors of the large-scale variation in the incidence of leaf-miner and gall-inducer herbivores as well as in variation in leaf nutritional quality. In sharp contrast, we found no evidence that plant chemical defences and bird attack rates were influenced by latitude or climatic factors, which conflicts with the dominant view in ecology (Moles & Ollerton, 2016;Roslin et al, 2017;Zvereva et al, 2019). Because unravelling causes of latitudinal variation in the strength of biological interactions is one of the common approaches for the prediction of biotic interactions under global warming (Verheyen et al, 2019), it is crucial that future studies simultaneously test for effects of latitude per se and climate on insect herbivory by different feeding guilds (Kozlov et al, 2017), as well as investigate the mechanisms underlying such effects.…”

“…Third, we cannot exclude that the lack of latitudinal trend in bird attack rates resulted from methodological limitations due to the fact we only exposed green dummy caterpillars, in low hanging branches. Birds depend more on food accessibility than abundance per se, so that the exact location of dummy caterpillars regarding factors such as edge, light contrast and shrubby understory may have modified the perception and the accessibility to the prey (Zvereva et al, 2019). Thus, the absence of a latitudinal trend in bird predation cannot be inferred only from geographical location.…”

“…Arthropod predators (e.g. ants, ladybirds) play an important role on herbivore populations and may respond to large-scale variation in climatic conditions at greater extent than vertebrate predators (Roslin et al, 2017;Zvereva et al, 2019). For example, a meta-analysis conducted by Rodríguez-Castañeda (2013) found that ant predation on herbivores significantly increase at higher temperatures and precipitations, indicating that plants growing under warmer and wetter conditions exhibit lower levels of insect herbivory.…”

“…Herbivore natural enemies, however, can drastically modify tritrophic interactions by suppressing herbivore populations or reducing herbivore feeding (Rosenheim, 1998;Maguire et al, 2015). In the few published studies exploring latitudinal patterns in natural enemy activity, authors have found no variation in parasitism (Dyer & Coley, 2002;Moreira et al, 2015), lower attack rates pressure by ants (Roslin et al, 2017), and higher (Zvereva et al, 2019) or no variation (Roslin et al, 2017) in attack rates by birds with increasing latitude. Thus, considering bottom-up and top-down forces simultaneously is crucial for a complete understanding of latitudinal clines in plant-herbivore interactions.…”

Variable colour patterns indicate multidimensional, intraspecific trait variation and ecological generalization in moths

“…The majority (ca 85%) of all insects are tropical or from the southern hemisphere (Stork ), and the majority (ca 90%) of Lepidoptera are dietary specialists (Forister et al ). Recent evidence suggests that latitudinal patterns of bird and arthropod predation on Lepidopteran larvae are opposites, and that selection for prey colouration may vary geographically and according to predator identity (Zvereva et al ). To our knowledge, however, it has not yet been systematically investigated whether tropical species of moths have less variable colour patterns.…”