Generalist flowers and phytophagous beetles in two tropical canopy trees: Resources for multitudes

Abstract

In the Republic of Panamá, phytophagous beetles were collected by hand and beating from superficially similar generalist blossoms of Nectandra umbrosa (Lauraceae) and Tapirira guianensis (Anacardiaceae), two phylogenetically distant Neotropical canopy trees. Beetles were sorted into three functional groups (guilds): general flower visitors, species developing in buds, and seed predators. Out of a total of 1,564 collected specimens belonging to 177 beetle species, 55 species or 31% were identifiable to specific epithet. These small- to medium-sized beetles belonged to four families: Cerambycidae, Chrysomelidae, Brentidae, and Curculionidae. A total of 723 beetles representing 121 species, and 841 beetles representing 121 species were recorded from N. umbrosa and T. guianensis, respectively. Of the beetles collected, 65 species were common to both trees, which equates to a similarity index value of 0.46 (Jaccard) or 0.34 (Sorensen). With respect to functional groups, there was no significant difference in the number of beetle species between the two tree species. Overall, beetle abundance patterns on flowers of the two trees are similar in terms of phytophagous beetle subfamily dominance. There are differences however, significantly more leaf beetles (Cryptocephalinae, Eumolpinae, Galerucinae) were collected per hour on T. guianensis than on N. umbrosa. Moreover, among beetles shared between the two tree species, Baridinae weevils showed a tendency to be more abundant on N. umbrosa. Nearly three-quarters of the flower feeders (72%) were shared between the two trees. The large overlap in beetle species between the two plant species suggests that the fauna is fairly general in terms of host use. We discuss the possible significance of our results to phytophagous beetle and host plant evolution. The combined effects of large species numbers, high abundance and broad diet breadth across generalist flowers of tropical canopy trees suggests that small- to medium-sized beetles play a crucial role in maintenance of species biodiversity and forest ecosystem function.