Abstract
Understanding the drivers of plant-insect interactions is still a key issue in terrestrial ecology. Here, we used 30 well-defined plant-herbivore assemblages to assess the effects of host plant phylogenetic isolation and origin (native vs. exotic) on the species richness, composition and specialization of the insect herbivore fauna on co-occurring plant species. We also tested for differences in such effects between assemblages composed exclusively of exophagous and endophagous herbivores. We found a consistent negative effect of the phylogenetic isolation of host plants on the richness, similarity and specialization of their insect herbivore faunas. Notably, except for Jaccard dissimilarity, the effect of phylogenetic isolation on the insect herbivore faunas did not vary between native and exotic plants. Our findings show that the phylogenetic isolation of host plants is a key factor that influences the richness, composition and specialization of their local herbivore faunas, regardless of the host plant origin.
Highlights
Ecologists have long been interested in why the species richness and composition of herbivores vary so much among co-occurring plant species [1,2,3,4]
Those studies with plantherbivore assemblages that met the following criteria were included in our study: 1) at least five plant and five insect species, totaling at least 10 species for each local species list; 2) the presence of both native and exotic plant species; 3) the occurrence of at least three exotic plant species; 4) an indication that all plants could potentially be consumed by any herbivorous insect in the list
Since we did not find any significant interactions between the effects of plant phylogenetic isolation and plant origin, all generalized linear mixed model (GLMM) models were subsequently fitted omitting the interaction term
Summary
Ecologists have long been interested in why the species richness and composition of herbivores vary so much among co-occurring plant species [1,2,3,4]. Several empirical studies have shown that both ecological and evolutionary features of host plants influence the diversity of their insect herbivores [5,6,7,8]. The major feature that determines which herbivores can consume a given host plant species is its set of defensive barriers [9,10]. A consequence of such constraints is that phylogenetically isolated host plants tend to be consumed by fewer species of insect herbivores [15,16,17].
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