Professor Princeton University Princeton, United States
Abstract: While much of the history of community ecology has focused on pairwise interactions between species, the potential for more complex interactions that only emerge in a multispecies context have long intrigued ecologists. Despite this interest, it is unknown the extent to which coexistence in diverse communities depends on multispecies interactions such as higher order interactions (HOIs). Progress on this topic has been limited in part by the logistical complexity of experiments required to estimate even simple 3-species HOIs, in addition a host of statistical and analytic challenges. Here we present results of field experiment designed to assess the overall impact of HOIs on species coexistence in a diverse community of serpentine-associated annual plants in coastal California. In particular, we focus on the question of how often higher order interactions arising from a competitor species reverse the direct pairwise effect that they have on a focal species. Using a suite of 9 species, we created experimental communities composed of sets of species grown together and in monoculture which allowed us to quantify the extent to which per capita growth rates of each species were impacted both by direct effects of competitors as well as by HOIs arising from the presence of each competitor species.
Preliminary analyses suggest that the aggregate impact of HOIs that arise from competitor species on the per capita growth rates of focal species can, in some cases, be sufficient enough to reverse the direct effects of the competitor on the focal, especially in cases where the direct effect on the focal species is strong. Future analyses will consider the functional trait basis of the HOI effects. Taken together, our experiment show a novel and tractable way to explore the aggregate effects of HOIs in a diverse community.
