Abstract
Plants constantly cope with insect herbivory, which is thought to be the evolutionary driver for the immense diversity of plant chemical defenses. Herbivorous insects are in turn restricted in host choice by the presence of plant chemical defense barriers. In this study, we analyzed whether butterfly host–plant patterns are determined by the presence of shared plant chemical defenses rather than by shared plant evolutionary history. Using correlation and phylogenetic statistics, we assessed the impact of host–plant chemical defense traits on shaping northwestern European butterfly assemblages at a macroevolutionary scale. Shared chemical defenses between plant families showed stronger correlation with overlap in butterfly assemblages than phylogenetic relatedness, providing evidence that chemical defenses may determine the assemblage of butterflies per plant family rather than shared evolutionary history. Although global congruence between butterflies and host–plant families was detected across the studied herbivory interactions, cophylogenetic statistics showed varying levels of congruence between butterflies and host chemical defense traits. We attribute this to the existence of multiple antiherbivore traits across plant families and the diversity of insect herbivory associations per plant family. Our results highlight the importance of plant chemical defenses in community ecology through their influence on insect assemblages.
Highlights
Plants and arthropod herbivores share a 420 million-year history of antagonistic coevolution (Labandeira, 1998)
Patterns varied in herbivore family-level analyses, we show that in the full interaction network increasing dissimilarity of plant chemical defenses corresponds with increased dissimilarity of butterfly species assemblage
In a certain community the presence of plant families with greater dissimilarity in chemical defense traits allows for greater diversity in butterfly assemblages
Summary
Plants and arthropod herbivores share a 420 million-year history of antagonistic coevolution (Labandeira, 1998). Ehrlich and Raven (1964) identified secondary metabolites as a form of antiherbivore defense, but more importantly gave rise to the “escape and radiate” scenario of speciation driven by chemical defenses (Endara et al, 2017; Farrell et al, 1991; Maron et al, 2019; Thompson, 1994). In this scenario, adaptation of insect herbivores to plant chemical defenses acts as a driver for the evolution of novel plant chemical defenses. We expect host plant chemical defenses to be an important predictor for butterfly–host use and expect to detect cophylogenetic interactions between butterflies and host plant chemical defenses
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