Geographical Variation in Community Divergence: Insights from Tropical Forest Monodominance by Ectomycorrhizal Trees*

Authors

Tadashi Fukami, Stanford University, StanfordFollow
Mifuyu Nakajima, Stanford University, Stanford
Claire Fortunel, University of California, Los Angeles
Paul V. Fine, University of California, Berkeley
Christopher Baraloto, Florida International University, Miami
Sabrina E. Russo, University of Nebraska - LincolnFollow
Kabir G. Peay, Stanford University, Stanford

ORCID IDs

http://orcid.org/0000-0001-5654-4785

http://orcid.org/0000-0001-7778-2029

Date of this Version

8-2017

Citation

Am. Nat. 2017. Vol. 190, pp. S105–S122.

http://dx.doi.org/10.5061/dryad.c0kr7.

Comments

2017 by The University of Chicago.

Abstract

Convergence occurs in both species traits and community structure, but how convergence at the two scales influences each other remains unclear. To address this question, we focus on tropical forest monodominance, in which a single, often ectomycorrhizal (EM) tree species occasionally dominates forest stands within a landscape otherwise characterized by diverse communities of arbuscular mycorrhizal (AM) trees. Such monodominance is a striking potential example of community divergence resulting in alternative stable states. However, it is observed only in some tropical regions. A diverse suite of AM and EM trees locally codominate forest stands elsewhere. We develop a hypothesis to explain this geographical difference using a simulation model of plant community assembly. Simulation results suggest that in a region with a few EM species (e.g., South America), EM trees experience strong selection for convergent traits that match the abiotic conditions of the environment. Consequently, EM species successfully compete against other species to form monodominant stands via positive plant-soil feedbacks. By contrast, in a region with many EM species (e.g., Southeast Asia), species maintain divergent traits because of complex plant-soil feedbacks, with no species having traits that enable monodominance. An analysis of plant trait data from Borneo and Peruvian Amazon was inconclusive. Overall, this work highlights the utility of geographical comparison in understanding the relationship between trait convergence and community convergence.