The distribution patterns of reptiles in the Riff region, northern Morocco

A biogeographical classification of reptiles in the Riff region (northern Morocco, Africa) was carried out to look for shared distribution patterns, here termed chorotypes. Baroni‐Urbani & Buser's similarity index was applied to the presence/absence data of reptiles in 10×10 km UTM (Universal Transverse Mercator) squares, and then UPGMA (Unweighted Pair‐Group Method using arithmetic average) was used to classify the species. A probabilistic method was employed to assess the statistical significance of the groups obtained. An ordination method, the Canonical Correspondence Analysis, was also used to study the distribution of the reptiles within a continuous framework.

A gradual longitudinal replacement of reptile species was found throughout the Riff, with no sharp discontinuities for the distributions of most of the species. This may be due to the biogeographical northward movement of the Saharan boundaries, which have not yet reached biogeographical equilibrium. Thus, Saharan reptiles enter the Riff region from the east, through the lower basin of the River Moulouya.

Seven reptile chorotypes were identified in the Riff, and these comprise Mediterranean species and others endemic to the Maghreb (the region that spans most of North‐western Africa, excluding the Sahara). These chorotypes have a western distribution, and are segregated from one another according to altitude. Historical and ecological processes can account for the distributions shared by these species, which have inhabited the Riff for longer than eastern reptiles.