Fig. 1

Illustration of the potential human impacts on functional structure. The functional spaces of a undisturbed community (blue solid line, A) and disturbed ones (yellow dashed lines) are compared. The global functional space is represented by the white area. Species are represented with dots. Blue dots correspond to species that are not affected by the disturbance, red crosses represent species sensitive to disturbance and yellow dots indicate species favoured by the disturbance. Note that, in all cases, species richness remains constant between the undisturbed (blue) and the disturbed (yellow) communities. Four non-exclusive differences with the functional space of a hypothetical undisturbed community (A) are proposed. B Hypothesis i: lower functional richness due to the absence of species with extreme traits (and the presence of more generalist species located in the center of the functional space). C Hypothesis ii: lower functional divergence due to the presence of generalist species located toward the center. D Hypothesis iii: lower functional evenness due to higher redundancy of species favoured by disturbance and lower redundancy of species sensitive to the disturbance. E Hypothesis iv: different functional identity of the disturbed community due to the presence of species with distinct traits compared to the undisturbed community, causing a shift in the functional structure toward lower values of axis 1