Opposing community assembly patterns for dominant and non-dominant plant species in herbaceous ecosystems globally

Full description

Biotic and abiotic factors interact with dominant plants —the locally most frequent or with the largest coverage— and non-dominant plants differently, partially because dominant plants modify the environment where non-dominant plants grow. For instance, if dominant plants compete strongly, they will deplete most resources, forcing non-dominant plants into a narrower niche space. Conversely, if dominant plants are constrained by the environment, they might not exhaust available resources but instead may ameliorate environmental stressors that usually limit non-dominants. Hence, the nature of interactions among non-dominant species could be modified by dominant species. Furthermore, these differences could translate into a disparity in the phylogenetic relatedness among dominants compared to the relatedness among non-dominants. By estimating phylogenetic dispersion in 78 grasslands across five continents, we found that dominant species were clustered (e.g., co-dominant grasses), suggesting dominant species are likely organized by environmental filtering, and that non-dominant species were either randomly assembled or overdispersed. Traits showed similar trends for those sites (<50%) with sufficient trait data. Furthermore, several lineages scattered in the phylogeny had more non-dominant species than expected at random, suggesting that traits common in non-dominants are phylogenetically conserved and have evolved multiple times. We also explored environmental drivers of the dominant/non-dominant disparity. We found different assembly patterns for dominants and non-dominants, consistent with asymmetries in assembly mechanisms. Among the different postulated mechanisms, our results suggest two complementary hypotheses seldom explored: (1) Non-dominant species include lineages adapted to thrive in the environment generated by dominant species. (2) Even when dominant species reduce resources to non-dominant ones, dominant species could have a stronger positive effect on some non-dominants by ameliorating environmental stressors affecting them, than by depleting resources and increasing the environmental stress to those non-dominants. These results show that the dominant/non-dominant asymmetry has ecological and evolutionary consequences fundamental to understand plant communities.

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External Organisations
University of Toronto; University of Minnesota; José Benito Vives de Andréis Marine and Coastal Research Institute; Escuela Politécnica Nacional; UNIVERSITY OF WASHINGTON; Archbold Biological Station; Trinity College Dublin; University of Lisbon; Queensland University of Technology; Queen's University; University of Pretoria; Utrecht University; University of Tartu; University of Bayreuth; International Business School Suzhou at Xi'an Jiaotong-Liverpool University; Smithsonian Environmental Research Center; Estonian University of Life Sciences; Doane University; University of Kentucky; Monash University; La Trobe University; National Scientific and Technical Research Council; Western Sydney University; University of Leeds; Algoma University; Instituto de Investigaciones en Biodiversidad y Medioambiente*; Murdoch University; University of Oulu

Associated Persons
John Dwyer (Creator)Carlos Alberto Arnillas (Creator); Elizabeth Borer (Creator); Eric Seabloom (Creator); Juan Alberti (Creator); Selene Baez (Creator); Jonathon Bakker (Creator); Elizabeth Boughton (Creator); Yvonne Buckley (Creator); Miguel Bugalho (Creator); Ian Donohue (Creator); Jennifer Firn (Creator); Riley Gridzak (Creator); Nicole Hagenah (Creator); Yann Hautier (Creator); Aveliina Helm (Creator); Anke Jentsch (Creator); Johannes (Jean) M H Knops (Creator); Kimberly Komatsu (Creator); Lauri Laanisto (Creator); Ramesh Laungani (Creator); Rebecca McCulley (Creator); Joslin Moore (Creator); John Morgan (Creator); Pablo Peri (Creator); Sally Power (Creator); Mahesh Sankaran (Creator); Brandon Schamp (Creator); Karina Speziale (Creator); Rachel Standish (Creator); Risto Virtanen (Creator); Marc Cadotte (Creator)