Linking vertebrate species richness to tree canopy height on a global scale

Aim In this paper we explore global links between tree canopy height and species richness of amphibians, birds and mammals. We follow the ideas first laid out by MacArthur and MacArthur in 1961 who found that in the eastern USA higher tree canopies supported more bird species, which they attributed to an increase of available niches as forests grow taller. We test if their findings can be generalized over large regions and other taxa by employing novel methods and using current datasets. Location Global Methods We used the global distribution maps of the three above taxa to infer species richness. Our tree canopy height information was derived from remotely sensed LiDAR data. The analysis was conducted globally and within biogeographical realms. We modeled richness, using tree canopy height and other environmental correlates, with generalized additive models and geographically weighted regressions. Results Globally, tree canopy height proved to be of lesser importance in explaining species richness patterns compared to other environmental drivers. Within biogeographical realms, tree canopy height was found to be a more important predictor of diversity in the N eotropic and A ustralian realms. Regional patterns show that tree canopy height has an important effect on diversity of amphibians throughout the world and in several tropical regions across taxa. N et P rimary P roductivity ( NPP ) explains more of the variation in richness both globally and within most regions. Main Conclusions Overall, tree canopy height is not an important predictor of diversity. However we highlight its relative importance in particular locations and settings.