Biogeographical zonation of African hornbills and their biotic and geographic characterisations

Abstract

We studied the geographic ranges of the 23 African hornbill species using countries as distribution units, to search for either groups of similar distributions (chorotypes) or gradual replacement of species as two different types of distribution patterns. We used a probabilistic classification method to distinguish between these two types of biogeographic patterns. Then we analysed the influence of climate, area, surface covered by different types of habitat, and human disturbance in each country, as well as biotic features of the species involving the habitat preference, feeding requirements and habits, body size, sexual dimorphism, and metabolic parameters, on the biogeographic patterns detected. We found that 20 species were significantly classified into three chorotypes. The western-central chorotype comprises nine species characterised by their preference for forest habitat and their low sexual body mass dimorphism. These species occur in 25 countries, characterised by their low range of temperatures. The eastern chorotype includes three species characterised by their preference for feeding on the ground and greater dimorphism in mass between the sexes. Seven countries, characterised by their high values of savanna and grassland surface area, constitute the geographic element of this chorotype. The southern chorotype involves the distribution of eight species characterised by their preference for montane and coastal forests or woodlands. Eighteen countries fall into this chorotype and are characterised by their low values of temperature in the coldest month and greater surface area of desert scrub and desert forest. The other three species replace each other mainly following a gradual pattern within the study area.