In: M. Cox, ed., Advances in Chrysomelidae I, Backhuys Publ., Leiden, pp. 343-360 (1999).

Host use by chrysomelid beetles feeding on Moraceae and Euphorbiaceae.

Vojtech Novotny, Yves Basset, G. Allen Samuelson, and Scott E. Miller

Abstract

The composition and host specificity of chrysomelid communities, feeding on 15 species of Moraceae and 15 of Euphorbiaceae in New Guinea is detailed. All 30 plant species were trees or shrubs, growing in rainforest and coastal habitats. Chrysomelids were collected alive and tested in the laboratory for feeding on the plant species from which they were obtained. Only specimens which fed were considered in the analyses. Sampling spanned almost over three years and 9,186 individuals from 93 species, belonging to 5 subfamilies were collected. Eumolpinae and Galerucinae dominated in terms of abundance and species richness. The foliage-feeding community consisted almost exclusively of adults, as eumolpine and most of the galerucine larvae were probably root-feeders. Species richness of chrysomelid communities varied from 1to 27 species per host plant species, and abundance from 8 to 1,462 individuals. Trees without diverse chrysomelid communities were fed upon mostly by generalists, whilst high density chrysomelid communities were dominated by specialists. Usually, Galerucinae were more host specific than Eumolpinae, but the overall host specificity of chrysomelids was rather low. In particular, there was a large overlap in the chrysomelid communities among congeneric plants. Most of the chrysomelid species fed on several congeneric hosts and were not strict monophages. Within Ficus, where such evaluation was possible, the similarity of chrysomelid communities did not reflect phylogenetic relationships among the host plants. Considered across plant genera, specialisation to a single genus was the most frequent case. Plant palatability, estimated from feeding experiments using a generalist species of weevil, was negatively correlated with the average host specificity in the chrysomelid community supported by this plant species; polyphagous chrysomelid species tended to be concentrated on palatable hosts. In conclusion, the patterns of host use by Eumolpinae and Galerucinae appear to be shifted towards oligophagy, in comparison with most of other subfamilies, feeding on Temperate herbs. Low host specificity of adults feeding on the foliage may be caused by the predominance of species with root-feeding larvae, and may explain the importance of plant palatability for the composition of chrysomelid communities.