Similarity in volatile communities leads to increased herbivory and greater tropical forest diversity

Abstract

Abstract. A longstanding paradigm in ecology is that there are positive associations between herbivore diversity, specialization, and plant species diversity, with a focus on taxonomic diversity. However, phytochemical diversity is also an informative metric, as insect herbivores interact with host plants not as taxonomic entities, but as sources of nutrients, primary metabolites, and mixtures of attractant and repellant chemicals. The present research examines herbivore responses to phytochemical diversity measured as volatile similarity in the tropical genus Piper. We quantified associations between naturally occurring volatile variation and herbivory by specialist and generalist insects. Intraspecific similarity of volatile compounds across individuals was associated with greater overall herbivory. A structural equation model supported the hypothesis that plot level volatile similarity caused greater herbivory by generalists, but not specialists, which led to increased understory plant richness. These results demonstrate that using volatiles as a functional diversity metric is informative for understanding tropical forest diversity and indicate that generalist herbivores contribute to the maintenance of diversity.

High specialization and limited structural change in plant‐herbivore networks along a successional chronosequence in tropical montane forest

“…Despite lower defensive investment in young secondary forest species (Poorter et al 2004, Endara andColey 2011), a greater diversity of host defenses may prevent herbivores from utilizing multiple hosts in more phylogenetically diverse secondary forest communities. Indeed, host plant chemical diversity was reported to affect herbivory in several cases (Salazar et al 2016, Massad et al 2017. Further, phylogenetic limitations to host use have been well documented, typically occurring on the level of host genus, for example; herbivorous communities of lowland forest in PNG (Weiblen et al 2006), and neotropical dry seasonal forest (Janzen 2003).…”

The many dimensions of phytochemical diversity: linking theory to practice

“…We use the term 'plant community variability hypotheses' to refer to a group of hypotheses that suggest fitness is increased when a plant is chemically divergent from neighbours in a community (i.e. the community has higher beta diversity; Salazar et al 2016b;Massad et al 2017). For example, the semiochemical diversity hypothesis (reviewed in Randlkofer et al 2010) suggests that herbivore host location is disrupted in complex chemical environments that include host and non-host species.…”

“…Beta diversity is an essential component of phytochemical diversity for plant interactions because it represents how organisms experience phytochemistryas variation in space and time (Wetzel & Thaler 2016;Salazar et al 2016a;Massad et al 2017;Pearse et al 2018) (Fig. 2).…”

Diversification rates, host plant shifts and an updated molecular phylogeny of Andean Eois moths (Lepidoptera: Geometridae)

“…Larvae of many species of Neotropical Eois are known to feed on Piper (Piperaceae) plants, in fact the moth genus is often being referred to as specialized feeders on Piper plants [ 17 , 40 ]. This frequently encountered trophic relationship of Eois with Piper has received considerable attention [ 12 , 14 , 17 , 40 , 41 ].…”