Assessing disturbance-sensitivity and generalism in mammals: Corroborating a hump-shaped relationship using a hemerobiotic approach

Hemeroby is an indicator widely used in plant ecology to evaluate the level of disturbance of the optimal habitat of a species. Hemeroby can be scaled on a range of ten point scores, higher scores of hemeroby meaning higher level of disturbance. In this study we applied two indicators of sensitivity to disturbance based on the concept of hemeroby: HSi (mean hemeroby score), calculated on the habitat types where each species occurs, and the recently proposed HHi (mean hemerobiotic entropy), i.e. the level of generalism of a species with respect to the range of levels of disturbance where the species occurs. Both indices are based on the position and range of species along a gradient of disturbance, from pristine to completely human-made habitats. From a recent regional atlas of mammals, it was possible to calculate the ecological preferences for a large number of habitat types for 36 common mammal species for Latium (Central Italy). From the occurrences of mammals in each habitat, we calculated the HSi (here rescaled: HSrescaled) and HHi indices. The relationship between habitat-related disturbance (HSrescaled) vs. generalism (HHi) of species showed a hump-shaped relationship peaking at intermediate levels of HSrescaled, suggesting that generalism is maximum at intermediate levels of disturbance and corroborating analogous results obtained for birds. Alien mammal species exhibited higher averaged values of HSi when compared to autochthonous species, supporting the evidence regarding the close relationship between alien species and more disturbed ecosystems. The application of the two indices to mammals could open new perspectives in conservation and management of species inhabiting a wide range of differently disturbed habitat types. (C) 2017 Elsevier Ltd. All rights reserved.