Tropical rainforests are teeming with life, and species inventories are far from complete. We know even less about the intricate ecological interactions that form the basis of tropical communities. One fascinating but poorly studied example is the host-symbiont network between army ants and their rich assemblages of arthropod guests. In issue 20 of Molecular Ecology, we studied the biodiversity and host specificity of such a network in a Costa Rican rainforest. Combining DNA barcoding with morphological identification, we discovered 62 species parasitizing the six available Eciton army ant host species, including beetles, flies, a millipede, and a silverfish. At least 14 of these species were new to science. Host specificity varied markedly, ranging from specialists parasitizing a single host, to host generalists occurring with all available host species. This highlights the immense diversity of army ant guests, both in terms of their species numbers and their ecological interactions with the ants. Like many of their cohabitants in tropical ecosystems, army ants are sensitive to habitat degradation, and extinction of the ants will go hand in hand with an extinction cascade of their numerous guests. We must therefore enhance our efforts to protect tropical rainforests to preserve such marvelous host-symbiont systems.

Article: Christoph von Beeren, Nico Blüthgen, Philipp O. Hoenle, Sebastian Pohl, Adrian Brückner, Alexey K. Tishechkin, Munetoshi Maruyama, Brian V. Brown, John M. Hash, W. E. Hall, Daniel J. C. Kronauer (2021). A remarkable legion of guests: Diversity and host specificity of army ant symbionts. Molecular Ecology, 30(20), 5229-5246. https://doi.org/10.1111/mec.16101

Summary written by Christoph von Beeren