Ecological Archives E094-267-A2

George Livingston, Yuexin Jiang, Jeremy W. Fox, Mathew A. Leibold. 2013. The dynamics of community assembly under sudden mixing in experimental microcosms. Ecology 94:2898–2906.

Appendix B. Methods for feeding trials and characterization of trophic structure.

We classified the majority of heterotrophic species into trophic categories based on a combination of feeding trials, the literature, and mouthpart size. We inoculated five individuals of each species into each of four culture conditions: (1) wheat seed only, (2) wheat seed and protist prey, (3) algae only, and (4) algae and protist prey. Based on culture experience and the literature, suitable potential prey were selected for each species (Appendix A). Petri dishes were filled with 30mL of COMBO and algae/prey were grown for one week prior to inoculation of focal species. Trials were not replicated and density was sampled using the same methods as in the main experiment after one or two weeks depending on when the species attained a countable density. Bacteria, prey protists, and algae were given one week to grow before species were inoculated. Species with growth on wheat seeds only were classified as bacterivores, those with growth on protist prey were classified as predators, those with growth on algae were classified as herbivores, and those with growth on some combination of bacteria, algae, and protists were classified as various types of omnivores (Fig. 2a, Appendix A).

Eight of the twenty-eight species in the trial failed to grow on at least one resource due either to strong Allee effects or low establishment success in mono-inoculation (i.e., co-inoculation with many other species increases establishment success). For these species, we inferred their trophic position from the literature, culturing experience, and cases in which they grew successfully in the feeding trial. All of these eight species are well described in the literature and assigning them to guilds was not ambiguous (supporting citations for each species in Appendix A).

Algae were classified as edible or inedible based on size. Edible species were less than 20µm in both width and length (generally 15µm maximum) and inedible species were greater than 20µm in at least one dimension.

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