Experimental dominant plant removal results in contrasting assembly for dominant and non-dominant plants

Understanding why communities appear deterministically dominated by relatively few species is an age-old debate in ecology. We hypothesised that the dominant and non-dominant species in a community are governed by different assembly mechanisms where environmental conditions influence dominant species more than non-dominant species. Further, dominant plants moderate the environment where non-dominant species thrive, diminishing the influence of environmental filtering and increasing the influence of limiting similarity for non-dominant species. We tested these hypotheses by removing two dominant species in five temperate meadows. We found that the composition of the non-dominants diverged while the new dominants converged over time. Phylogenetic analyses suggested that habitat filtering and limiting similarity drove the new dominant species simultaneously. Conversely, non-dominant community assembly appeared more unpredictable. These suggest that dominant species converged towards a predictable environmentally driven optimum, while non-dominant species thrive in a moderated habitat, which probably reduced non-dominant species predictability.