Beetle diversity subsists on flower resources

What is it about?

By means of a large tower crane, we observed and collected beetles in the Amazonian rainforest during the day and night for a full year. In total, we collected 6698 adult beetles representing 859 species from the canopies of 23 tree species. The majority of these beetles (647 species; 75.3%) were collected on flowering trees; 527 beetle species in 41 families were found exclusively associated with flowers. Particularly, mass-flowering trees with small white flowers of a generalised morphology supported a speciose beetle community. In total, 406 flower-visiting beetle species (63%) were collected on only three out of 20 flowering tree species. A single tree species attracted 260 different beetle species. On average, there were 26.35 flower-visiting beetle species per tree species. Extrapolating this average on the estimated 16,000 Amazonian tree species there could be 421,600 beetle species utilising flowers in the Amazonian rainforest. This indicates beetles could be by far the most species-rich flower-visiting insects.

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Why is it important?

Flower-visiting beetle assemblages are restricted to the flowering season. Thus, food resources such as flowers mediate the presence, timing and diversity of beetle communities in tropical forest canopies. Moreover, the beetle species visit flowering trees only during a distinct time of the day which coincides with their activity on their host trees. This results in a high faunal turnover of beetle species on tropical tree canopies such as found in many early fogging studies. The aggregation of speciose beetle assemblages on flowering trees and their specificity to flower resources strongly indicate that the enormous diversity of canopy beetles in Amazonian tropical rainforests is due mainly to flowers. Particularly mass-flowering trees with small white flowers of the generalist syndrome play a particularly crucial role in assembly and nourishment of this megadiverse beetle community. Beetles are an underestimated pollinator taxon. They are the most species-rich insect order on Earth with about 400,000 known species. In general, beetles are considered fourth in terms of pollinator importance, but they have been found often as the second most important visitor group in tropical ecosystems. Beetles are among the earliest pollinators or even the oldest ones and specialised beetle-pollinated flowers were apparent by the Cretaceous.