Context dependency of biotic interactions and its relation to plant rarity

Anne Kempel,Daniel Prati,Hugo Vincent,Markus Fischer,Amanda Taylor

doi:10.1111/ddi.13050

Abstract

AbstractAimBiotic interactions can determine rarity and commonness of species, however, evidence that rare and common species respond differently to biotic stress is scarce. This is because biotic interactions are notoriously context dependent and traits leading to success in one habitat might be costly or unimportant in another. We aim to identify plant characteristics that are related to biotic interactions and may drive patterns of rarity and commonness, taking environmental context into account.LocationSwitzerland.MethodsIn a multispecies experiment, we compared the response to biotic interactions of 19 rare and 21 widespread congeneric plant species in Switzerland, while also accounting for variation in environmental conditions of the species' origin.ResultsOur results restrict the long‐standing hypothesis that widespread species are superior competitors to rare species to only those species originating from resource‐rich habitats, in which competition is usually strong. Tolerance to herbivory and ambient herbivore damage, on the other hand, did not differ between widespread and rare species. In accordance with the resource‐availability hypothesis, widespread species from resource‐rich habitats where more damaged by herbivores (less defended) than widespread species from resource‐poor habitats—such a growth‐defence trade‐off was lacking in rare species. This indicates that the evolutionary important trade‐off between traits increasing competitive ability and defence is present in widespread species but may have been lost or never evolved in rare species.Main conclusionsOur results indicate that biotic interactions, above all competition, might indeed set range limits and underlines the importance of including context dependency in studies comparing traits of common and rare or invasive and non‐invasive species.

Highlights

Understanding why some species are rare while others are widespread or invasive remains a fascinating question in ecology spanning decades (Baker, 1965; Gaston, 1994)
In our multispecies experiment, using 40 plant species differing in regional rarity and originating from contrasting habitats, we show that taking into account phylogenetic and environmental context dependency is important when comparing widespread and rare or invasive and non-invasive species
In our experiment, using 40 plant species differing in regional rarity and originating from a wide range of habitats, we show that widespread species suffered less from competition than rare species, but only when both widespread and rare species originated from nutrient-rich and moist habitats

Summary

Introduction

Understanding why some species are rare while others are widespread or invasive remains a fascinating question in ecology spanning decades (Baker, 1965; Gaston, 1994). Attempts to identify traits or characteristics of rare and widespread or invasive species were often not successful or revealed contradictory results One explanation for this is that certain plant traits or characteristics may benefit a species in some habitats, but in others may be costly (as they often trade-off, Kempel, Schädler, Chrobock, Fischer, & Kleunen, 2011) or unimportant (Darwin, 1859; Louthan, Doak, & Angert, 2015). This context dependency has frequently been invoked to explain that the drivers of plant success vary along environmental gradients (Funk & Cornwell, 2013; van Kleunen, Dawson, & Maurel, 2015; Kueffer, Pyšek, & Richardson, 2013). Context dependency has rarely been considered in experimental studies comparing characteristics of plants of widespread and rare, or invasive and non-invasive species

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