Abstract

Allozyme variation and evolutionary relationship in species of the genus Microlophus of the peruvianus group from 11 localities in Chile and southern Perú were determined. Two external groups (M. occipitalis and M. thoracicus, both from northern Perú), were considered to polarize character states in a cladistics analysis. A total of 22 presumptive loci were analysed, of which 18 were variables. The results obtained suggests the presence of three species of Microlophus in southern Peril and northern Chile. Two species inhabit intertidal areas; one correspond to M. quadrivittatus which extends from Islay in Perú (16°59, S, 72°06, W) to Antofagasta in Chile (23°40, S, 70°26, W). The second species, M. atacamensis, is distribuited from the south of Antofagasta to Tres Playitas in Chile (28° 28' S, 71°14' W). The third species corresponds to M. theresioides, which is distribuited in the chilean desert, in Pica (20°30' S, 69°20' W), Huayca (20°11' S, 69°08' W), and Mamiña (20°04' S, 69°13' W), and probably extends to the coastal range of the Chilean desert at this latitude. The taxonomic arrangement proposed is according to Rogers genetic identity levels, where the respective dendrogram clustered populations in three nodes, one for each species. Phylogenetic analysis confirms the existence of three clades corresponding to species suggested by phenetic analysis. We did not detect evidence of monophily of both coastal species. This indicates that M. atacamensis is the sister taxon of M. quadrivittatus - M. theresioides clade. According to this, the adaptation to an intertidal habitat could have originated more than once in the evolutionary history of Microlophus of the peruvianus group. Another explanation is that this adaptation is plesiomorphic within the group analysed.