Land Unit definition for potential distribution of endangered species

In Europe several mapping techniques exist to lay out plant distribution. Most of them, however, are focused on actual and not on potential species distribution range. Spatial predictions become more important for rare and endangered taxa because their conservation is related to existing as well as potential biotopes. The large part of detailed distribution models applies advanced statistics on a large data-set of environmental variables. Data-input availability limits the choice of the prediction model for species distribution and application of results in a detailed scale. Distribution pattern accuracy determinates its applicability in environmental management (for tracing edges, defining protected areas, etc.). A simple distribution model for endangered taxa is outlined here, based on ecologically homogenous units (land-units) defined with a deductive process. Land-units defined with a hierarchical classification approach are usually employed for modelling phytocoenosis distribution. The spatial model used is based on main structural factors: bioclimate, lithology and landforms. The data set is implemented with land-use information. This model was tested with two case study in Sicily: Erica sicula subsp. sicula and Abies nebrodensis. The former is nowadays confined only to Mt. Cofano (W Sicily) but was reported also from Mt. San Giuliano (Erice) and Marettimo Island (W Sicily), the latter occurs with a natural population of 32 individuals in the Madonie Mountains (N Sicily). This predicting method allowed to identify suitable areas for reintroduction or where the taxa could still occur and floristic investigation should be focused.