Indirect interactions in terrestrial plant communities: emerging patterns and research gaps

Abstract

Abstract. Indirect interactions occur when the effect of one species on another is mediated by a third species. These interactions occur in most multi-species assemblages and are diverse in their mechanistic pathways. The interest in indirect interactions has increased exponentially over the past three decades, in recognition of their importance in determining plant community dynamics and promoting species coexistence. Here, we review the literature on indirect interactions among plants published since 1990, using a novel synthetic framework that accounts for and classifies intervening species and mechanisms within trophic networks. The objectives of this review are: (1) to identify the geographical regions and ecosystem types where indirect interactions have been examined; (2) to summarize the information on the number of trophic levels examined in studies of indirect interactions; (3) to test whether the frequency of indirect interactions varies across environmental gradients; and (4) to identify the experimental approaches most commonly used in studies of indirect interactions. Studies examining indirect interactions in plants have been conducted primarily in the Northern Hemisphere, with a focus on grasslands and forests. The majority of studies (67%) examined two trophic levels. Indirect facilitation and apparent competition are the interactions that have been most frequently examined, with the latter being reported more frequently in relatively productive environments. Other indirect interactions reported include associational resistance, exploitative competition or facilitation, shared defenses, and trophic cascades. Generally, field experiments tested indirect interactions based on single target species. While the majority of studies on indirect interactions dealt with basic ecology issues, several studies have dealt with such interactions in the context of biological invasions (18%) and rangeland management (12%). This review allowed us identifying a number of research needs, including the study of non-feeding interactions and that for more realistic complex designs, explicitly testing indirect interactions across different trophic levels, in geographical regions that have been under-examined to date, and in stressful ecosystems.

Evidence for a stochastic geometry of biodiversity: the effects of species abundance, richness and intraspecific clustering

“…These processes can be diffused and undetectable at the species pair level, that is, when exploring only species pair patterns. Indirect interactions are assumed to play a key role in community assemblies by promoting diversity and coexistence (Sotomayor & Lortie ). In fact, in a related study, we found that although interspecific interactions did not appear to be driving the local distribution of the species in the community, this pattern did not necessarily scale up to the community level, where the species richness was well structured in multispecies clumps (Chacón‐Labella, de la Cruz & Escudero ).…”

No evidence for trade‐offs in plant responses to consumer food web manipulations

“…, , Moore et al. , Sotomayor and Lortie ). As a result of these indirect interactions, the effects of natural enemies on a species may depend as much on the community context of a host as on its inherent resistance or tolerance to an enemy (Holt et al.…”

“…As a result of these indirect interactions, the effects of natural enemies on a species may depend as much on the community context of a host as on its inherent resistance or tolerance to an enemy (Holt et al. , , Sotomayor and Lortie ). For example, the presence of a highly competent host in a community may increase pathogen prevalence (i.e., the spillover effect; Power and Mitchell ) and may ultimately reverse the competitive hierarchy among plant species (Borer et al.…”

Indirect interactions between crops and natural vegetation through flower visitors: the importance of temporal as well as spatial spillover

“…The interactions between these role-players influence not only the organisms involved, but ecosystem functioning, as they combine to form complex networks at a range of scales . As the Anthropocene advances, indirect interactions (that is, the effects of one species on another, mediated by a third species) via pollination of terrestrial plants emerges as key to maintenance of biodiversity, ecosystem function, and agricultural production Sauve et al, 2016;Sotomayor and Lortie, 2015). This is because perturbations can have unforeseen consequences for a number of species via shared resources.…”

“…To date, most studies relating landuse to spillover effects have occurred in temperate, ecologically-transformed regions in the northern hemisphere (Henri et al, 2015;Sotomayor and Lortie, 2015). In addition, approximately half of the data used in thirteen recent meta-analyses on global pollination ecology were collected from only 5 developed countries, with the entire African continent contributing only 4% of the data (Archer et al, 2014).…”