Tree resin composition, collection behavior and selective filters shape chemical profiles of tropical bees (Apidae: Meliponini).

Sara D Leonhardt,Nico Blüthgen,Thomas Schmitt,Nigel E Raine

doi:10.1371/journal.pone.0023445

Sara D Leonhardt, Nico Blüthgen + Show 2 more

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https://doi.org/10.1371/journal.pone.0023445

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Journal: PloS one	Publication Date: Aug 8, 2011
Citations: 80	License type: CC BY 4.0

Affiliation: University of Würzburg, University of Freiburg

Abstract

The diversity of species is striking, but can be far exceeded by the chemical diversity of compounds collected, produced or used by them. Here, we relate the specificity of plant-consumer interactions to chemical diversity applying a comparative network analysis to both levels. Chemical diversity was explored for interactions between tropical stingless bees and plant resins, which bees collect for nest construction and to deter predators and microbes. Resins also function as an environmental source for terpenes that serve as appeasement allomones and protection against predators when accumulated on the bees' body surfaces. To unravel the origin of the bees' complex chemical profiles, we investigated resin collection and the processing of resin-derived terpenes. We therefore analyzed chemical networks of tree resins, foraging networks of resin collecting bees, and their acquired chemical networks. We revealed that 113 terpenes in nests of six bee species and 83 on their body surfaces comprised a subset of the 1,117 compounds found in resins from seven tree species. Sesquiterpenes were the most variable class of terpenes. Albeit widely present in tree resins, they were only found on the body surface of some species, but entirely lacking in others. Moreover, whereas the nest profile of Tetragonula melanocephala contained sesquiterpenes, its surface profile did not. Stingless bees showed a generalized collecting behavior among resin sources, and only a hitherto undescribed species-specific “filtering” of resin-derived terpenes can explain the variation in chemical profiles of nests and body surfaces from different species. The tight relationship between bees and tree resins of a large variety of species elucidates why the bees' surfaces contain a much higher chemodiversity than other hymenopterans.

Highlights

Biodiversity is considered a crucial feature of ecosystems worldwide, by, for instance, providing a variety of organisms that maintain ecosystem functioning and services [1]
Stingless bees are generalized resin collectors with species-specific compositions of terpenes derived from plant resins in their cuticular profiles [20] and their nest profiles
Most of these terpenes could be directly attributed to resin from trees in their habitat even in the small set of tree species studied, but comprised only a subset of the vast amount of terpenes generally found in the tree resins sampled

Summary

Introduction

Biodiversity is considered a crucial feature of ecosystems worldwide, by, for instance, providing a variety of organisms that maintain ecosystem functioning and services [1]. We used a plant-insect interaction network to unravel the origin of a rather neglected kind of diversity: chemical diversity – describing the heterogeneity of chemical compounds produced or acquired and used by organisms. Plants produce secondary metabolites to defend themselves against herbivores [5] or to attract mutualists, such as parasitoids [6,7] and pollinators [8,9,10,11]. The composition of secondary metabolites may vary across seasons [12], developmental states [12,13], species [11,14], individuals, different plant parts of the same individual [15,16] or in response to herbivore attack [6,7]

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