Evolutionary history of grazing and resources determine herbivore exclusion effects on plant diversity

Price, J. and Sitters, J. and Ohlert, Timothy and Tognetti, P.M. and Brown, C and Seabloom, Eric W. and Borer, Elizabeth and Prober, S. and Bakker, L. and MacDougall, Andrew S. and Yahdjian, L. and Gruner, Daniel S. and Olde Venterink, Harry and Barrio, Isabel C. and Graff, P. and Bagchi, Sumanta and Arnillas, C.A. and Bakker, J.D. and Blumenthal, Dana M. and Boughton, Elizabeth H. and Brudvig, Lars A. and Bugalho, Miguel N. and Cadotte, Marc and Caldeira, M.C. and Dickman, C. R. and Donohue, Ian and Gregory, S. and Hautier, Y. and Jónsdóttir, Ingibjörg S. and Lannes, L.S. and Mcculley, Rebecca and Moore, Joslin L. and Power, S.A. and Risch, A. and Schütz, Martin and Standish, Rachel J. and Stevens, Carly and Veen, G.F. and Virtanen, Risto and Wardle, Glenda M. (2022) Evolutionary history of grazing and resources determine herbivore exclusion effects on plant diversity. Nature Ecology and Evolution, 6. 1290–1298. ISSN 2397-334X

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Abstract

Ecological models predict that the effects of mammalian herbivore exclusion on plant diversity depend on resource availability and plant exposure to ungulate grazing over evolutionary time. Using an experiment replicated in 57 grasslands on six continents, with contrasting evolutionary history of grazing, we tested how resources (mean annual precipitation and soil nutrients) determine herbivore exclusion effects on plant diversity, richness and evenness. Here we show that at sites with a long history of ungulate grazing, herbivore exclusion reduced plant diversity by reducing both richness and evenness and the responses of richness and diversity to herbivore exclusion decreased with mean annual precipitation. At sites with a short history of grazing, the effects of herbivore exclusion were not related to precipitation but differed for native and exotic plant richness. Thus, plant species’ evolutionary history of grazing continues to shape the response of the world’s grasslands to changing mammalian herbivory.