Basset, Y., Cizek, L., Cuénoud, P., Didham, R.K., Guilhaumon, F., Missa, O., Novotny, V., Ødegaard, F., Roslin, T., Schmidl, J., Tishechkin, A.K., Winchester, N.N., Roubik, D.W., Aberlenc, H.P., Bail, J., Barrios, H., Bridle, J.R., Castaño-Meneses, G., Corbara, B., Curletti, G., Rocha, W.D., De Bakker, D., Delabie, J.H.C., Dejean, A., Fagan, L.L., Floren, A., Kitching, R.L., Medianero, E., Miller, S.E., Oliveira, E.G., Orivel, J., Pollet, M., Rapp, M., Ribeiro, S.P., Roisin, Y., Schmidt, J.B., Sørensen, L., Leponce, M.

Most eukaryotic organisms are arthropods. Yet, their diversity in rich terrestrial ecosystems is
still unknown. Here we produce tangible estimates of the total species richness of arthropods in
a tropical rainforest. Using a comprehensive range of structured protocols, we sampled the
phylogenetic breadth of arthropod taxa from the soil to the forest canopy in the San Lorenzo forest,
Panama. We collected 6144 arthropod species from 0.48 hectare and extrapolated total species
richness to larger areas on the basis of competing models. The whole 6000-hectare forest reserve
most likely sustains 25,000 arthropod species. Notably, just 1 hectare of rainforest yields >60% of
the arthropod biodiversity held in the wider landscape. Models based on plant diversity fitted the
accumulated species richness of both herbivore and nonherbivore taxa exceptionally well. This
lends credence to global estimates of arthropod biodiversity developed from plant models.