IBP′: A New Index to Estimate Biogeographical Peculiarity

The biogeographical peculiarity of a given geographical area is directly linked to the number of its endemic species. This paper aims to formulate an index directly linked to the biogeographical peculiarity of an area. A graphical model and an index of the biogeographical peculiarity are proposed, based on a cumulative sum (i.e., including all the amounts that were added previously). An example of the computations is proposed, based on the number of different types of geographical ranges (i.e., chorotypes) characterizing two different ecosystems; their biogeographical peculiarity of was evaluated on the basis of presence versus absence of carabid species. Both the graphical model and the index mirrored the different faunistic compositions of the ecosystems, because the index reached a higher value where more endemic species have been found. Our investigation has found a new method for evaluating the biogeographical peculiarity of a given area or biota in a simple way. The index could be used for either conservation biogeography (e.g., monitoring of biotic homogenization) or for theoretical studies integrating ecology and biogeography. 1. Introduction The geographical distribution of living organisms is the result of cladogenesis combined with palaeogeographic events (e.g., continental drift) and palaeoclimatic events (e.g., ice ages) [1–3]. For a discussion on cladistic versus evolutionist see [4]. Furthermore, living organisms, whether or not they are undergoing the process of speciation, have to deal with changeable environmental factors (e.g., biotic interactions, human factors, realized ecological niche, and dispersal ability), where their power of adaptation is a decisive factor in determining their present distribution range [5]. The types of geographical range in a given area characterize the natural resources of that area not only taxonomically but also ecologically, because the geographical range of a species is directly linked to several morphofunctional traits of that species, which allow it to survive in a particular environment for sufficient time to cope with the constraints of evolution [6–9]. This is why the species distribution range is not simply a matter of squared kilometers, while it is reasonable to regard it as a biological characteristic of a species [10, 11]. This way it is an important parameter to be taken into account, for example, in the evaluation of conservation protocols [12–15]. Similarities among geographical ranges make it possible to classify them into types called chorotypes, the sum of which gives the chorological