George Mercer Award

Lynette H. L. Loke and Ryan A. Chisholm

ESA presents the 2025 George Mercer Award to Lynette H. L. Loke and Ryan A. Chisholm, authors of “Unveiling the Transition from Niche to Dispersal Assembly in Ecology,” published in Nature June 7, 2023.

The George Mercer Award was established in 1948 and is awarded annually for an outstanding ecological research paper published within the past two years by a younger researcher (the lead author of the paper must be 40 years of age or younger at the time of publication).

The paper recognized by this year’s award advances our understanding of the effects of immigration on species coexistence in intertidal communities. Previous theories suggested that niches will dictate the maximum numbers of species that can coexist in a community, and that only very slow arrival of new species will keep communities from reaching this maximum. Loke and Chisholm conducted an extensive field experiment with a novel community assembly design to manipulate immigration rates, then went further by combining these results with a model to test alternative hypotheses for community assembly.

Using a new theory, the authors showed that the number of niches in a habitat sets a low floor rather than a high ceiling on the number of coexisting species — and that there appears to be no ceiling at all if new species arrive rapidly enough. The results support the view that most species coexist transiently, not stably, and that coexistence is maintained by ongoing immigration.

Deftly integrating field experiments with clear hypotheses and mathematical modeling, this study provides novel insights into an ecological question that has been debated for decades. The results of the paper advance our understanding of the forces structuring ecological communities, and the authors combine theory and empirical evidence in a creative and exceptionally well-written way.

Credit: https://esa.org/blog/2025/05/14/ecological-society-of-america-announces…