## 2 Materials and Methods
### Calculation for the Excluded Areas  
To exclude the areas that are within the distance of 6000 m from any apiary, the buffer tool was applied. \"Buffer\" is one of the most important geoprocessing operations and frequently used in GIS projects [14]. A buffer increases a feature's area by a given radius, exactly following its original geometry (point, line, or polygon). For the calculation of the areas to exclude, BDNA data were used, and in particular all the apiaries as of December 2019. A total of 143,738 apiaries were extracted and used to calculate the buffer areas (Figure 3a). The set of all calculated buffers (Figure 3b) was then used to exclude these portions of territory from the national surface (due to the presence of apiaries within 6000 m radius). To exclude the wetland areas an attribute selection function was used [14]. The CLC attribute value equal to 4 (humid environment) or 5 (water environment) were used as filter option and the resulting geospatial data were used to exclude these portions of territory. To exclude the areas above 1500 m of altitude the operation performed mixed raster map algebra instruments with the vector functions [14]. The first step was to apply a filter to the pixel values greater than 1500 m. The next step was to convert the selected pixel into a vector geospatial data (raster-to-vector operation). The resulting geospatial data were used to exclude the portions of territory above 1500 m.  
Figure 3: (**a**) Around each apiary present in the BDNA a buffer area was created with a radius of 6 km which corresponds to a surface of 113 km\({}^{2}\). The black dot indicates an apiary in the BDNA, the red circle the area resulting from applying a 6 km radius, the pink area represents the excluded area, and the white area the potentially suitable area. (**b**) The resulting excluded area due to the presence of apiaries is spatially represented by a series of buffers. (**c**) The area not included in the buffers, and not excluded by other criteria (in red), was considered as “suitable area for the establishment of mating stations”. Figure 2: These maps are print screens obtained from the Italian geoportal ([[http://www.pcn.miambiente.it/viewer/index.php?services=dtm_20m](http://www.pcn.miambiente.it/viewer/index.php?services=dtm_20m)]([http://www.pcn.miambiente.it/viewer/index.php?services=dtm_20m](http://www.pcn.miambiente.it/viewer/index.php?services=dtm_20m)), accessed on 31 May 2021). The left image is the representation of the territory derived from satellite data, where it is visually possible to recognize the territory’s orography. The right image is the DTM image of the same portion of territory. The image is in reality geospatial data composed of pixels whose values represent the altitude. A chromatic scale, which range from green to brown, is used to represent the altitude variation. To exclude the areas within the distance of 1500 m from the Italian boundary, the already above mentioned buffer operation was used. All the resulting excluded areas were than merged together by a union operation in order to obtain the total excluded areas. To derive the portions of potentially suitable areas for the establishment of mating stations, a difference operation between the total Italian territory and the total excluded areas was made. As shown in Figure 3c, the total area is made up by the sum of portions of geographically distinct suitable areas. All operations were carried out using the ESRIT ArchMap 10.5.1 GIS software ([[http://desktop.arcgis.com/en/arcmap/](http://desktop.arcgis.com/en/arcmap/)]([http://desktop.arcgis.com/en/arcmap/](http://desktop.arcgis.com/en/arcmap/)), accessed on 10 May 2021). ArcGIS is a GIS for working with maps and geographic information maintained by the Environmental Systems Research Institute (Esri).