Taxonomic Nightmare: Hard Species Delimitation in Liolaemus (Squamata: Liolaemidae) Lizards of the Peruvian High Andean Plateau with a Description of a New Cryptic Species

Liolaemus species are the only lizards inhabiting the cold and hypoxic environments of the high Andean plateau. However, delimiting species within the Liolaemus montanus group across this region remains exceptionally challenging. Two taxonomically difficult groups in this area, the L. annectens and L. signifer complexes, comprise valid species and unassigned populations that require extensive taxonomic revision using modern species delimitation approaches. In this study, we perform phylogenetic, single-locus species delimitation and nuclear network analyses on these complexes. Our results show that within the L. annectens and L. signifer complexes, three and one lineages, respectively, are congruent with mitochondrial evidence and at least one haplotype network. L. annectens is supported by mitochondrial evidence but lacks unique haplotypes in both nuclear networks, and L. signifer shows inconclusive support by both mitochondrial and nuclear evidence. Based on these molecular results and morphological analyses, we describe a new Andean cryptic species, Liolaemus arequipensis sp. nov. from southern Peru.