Plio–Pleistocene range dynamics of the spotted sand lizard (Pedioplanis lineoocellata) sheds light on taxonomic uncertainty

Although the subspecies concept remains contentious, it has value in biology. Historically, subspecies have been described using morphology or ecology, often ignoring plasticity or genetics, leading to taxonomic conflicts. This is exemplified by the spotted sand lizard (Pedioplanis lineoocellata), where subspecies were described from variable traits in few specimens. We reassessed these subspecies using an evolutionary framework, analysing > 200 samples with nine microsatellites, sequences (autosomal, mitochondrial), and morphological traits. The subspecies were not monophyletic but genetic clustering was associated with ecoregions. Only the subspecies Pedioplanis lineoocellata inocellata had significant morphological ­differences from the others. The ancestral area reconstruction shows that geographic-genetic patterns are a complex layering of Plio–Pleistocene range dynamics, reflected in recent gene flow across much of the distribution despite deep mtDNA divergences. The association of genetic groups with ecoregions suggests that climate-driven biome change influenced expansion–contraction events. Our work highlights the need for multi-dimensional taxonomic classification as using any single line of evidence may provide an incomplete picture, potentially misdirecting research and conservation efforts.