Elevational gradients affect the production of plant secondary metabolites through changes in both biotic and abiotic conditions. Previous studies have suggested both elevational increases and decreases in host-plant chemical defences. We analysed the correlation of alkaloids and polyphenols with elevation in a community of nine Ficus species along a continuously forested elevational gradient in Papua New Guinea. We sampled 204 insect species feeding on the leaves of these hosts and correlated their community structure to the focal compounds. Additionally, we explored species richness of folivorous mammals along the gradient. When we accounted for Ficus species identity, we found a general elevational increase in flavonoids and alkaloids. Elevational trends in non-flavonol polyphenols were less pronounced or showed non-linear correlations with elevation. Polyphenols responded more strongly to changes in temperature and humidity than alkaloids. The abundance of insect herbivores decreased with elevation, while the species richness of folivorous mammals showed an elevational increase. Insect community structure was affected mainly by alkaloid concentration and diversity. Although our results show an elevational increase in several groups of metabolites, the drivers behind these trends likely differ. Flavonoids may provide figs with protection against abiotic stressors. In contrast, alkaloids affect insect herbivores and may provide protection against mammalian herbivores and pathogens. Concurrent analysis of multiple compound groups alongside ecological data is an important approach for understanding the selective landscape that shapes plant defences.

Bell Museum Department of Plant and Microbial Biology University of Minnesota 140 Gortner Laboratory 1479 Gortner Avenue Saint Paul MN 55108 USA

Biology Centre Institute of Entomology Czech Academy of Sciences Branisovska 31 37005 Ceske Budejovice Czech Republic Faculty of Science University of South Bohemia Branisovska 1760 Ceske Budejovice 37005 Czech Republic

Biology Centre Institute of Entomology Czech Academy of Sciences Branisovska 31 37005 Ceske Budejovice Czech Republic Faculty of Science University of South Bohemia Branisovska 1760 Ceske Budejovice 37005 Czech Republic Department of Crop and Environment Sciences Harper Adams University Newport Shropshire TF10 8NB UK

Biology Centre Institute of Entomology Czech Academy of Sciences Branisovska 31 37005 Ceske Budejovice Czech Republic Faculty of Science University of South Bohemia Branisovska 1760 Ceske Budejovice 37005 Czech Republic Scion The New Zealand Forest Research Institute 49 Sala Street Rotorua New Zealand

Biology Centre Institute of Entomology Czech Academy of Sciences Branisovska 31 37005 Ceske Budejovice Czech Republic Griffith School of Environment Griffith University Mount Gravatt Queensland Australia

Biology Centre Institute of Entomology Czech Academy of Sciences Branisovska 31 37005 Ceske Budejovice Czech Republic Molecular Interaction Ecology Group German Centre for Integrative Biodiversity Research Halle Jena Leipzig Deutscher Platz 5e 04103 Leipzig Germany

National Museum of Natural History Smithsonian Institution 10th St and Constitution Ave NW Washington DC 20560 USA

Natural Chemistry Research Group Department of Chemistry University of Turku FI 20500 Turku Finland

The New Guinea Binatang Research Center P O Box 604 Madang Papua New Guinea

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