Genetics and fuzzy logic unravel the historical biogeography of European rabbit subspecies in the species' native range

The European rabbit Oryctolagus cuniculus is native to the lberian Península (IP), where the two known rabbit subspecies occur. Previous studies have suggested that O.c. cuniculus distribution extends towards the north-east of the IP, while O.c. algirus is restricted to south-westem regions; a transition area crosses the IP from the north-west to the south-east. Here, we revisited rabbit subspecies distribution to define with greater precision historical distribution areas, identifying the potential expansion cores and evaluating the spatial interaction between both subspecies expansion waves. We used different diagnostic loci located on mitochondrial and nuclear DNA to classify in any of the subspecies 4500 rabbits from 197 populations distributed throughout the IP. Using populations where all the rabbits were either O.c. cuniculus or O.c. algirus, we determined the spatial structure of the two molecules independently, by using a trend surface analysis based on favourability functions. We then combined the different spatial structures using fuzzy logic operations. Two areas in the Guadalquivir and Ebro valleys were identified as respective expansion cores. In comparison to previous studies, we found an increase in the distribution range of O.c. algirus to the northwest anda shift of the transition zone eastwards in its northern area. Our results suggest that competitive exclusion may ha ve a greater role than expected in regulating the expansion of both subspecies. The spatial structure of these genes reflects, and thus may be used to unravel, the historical biogeography of these subspecies, provided that we possess appropriate analytical tools, such as fuzzy logic.