Geographic variation in colour and spot patterns in Dwarf Caiman, Paleosuchus palpebrosus (Cuvier, 1807) in Brazil

Colour variation in crocodilians is associated with size, environment and genetic structure, but little is known about colour variation in the genus Paleosuchus (Alligatoridae). Different genetic lineages of Paleosuchus palpebrosus (Dwarf caiman) occupy different environments throughout the species extensive distribution, and all are cryptically coloured. We captured 187 P. palpebrosus and recorded their head colour from four genetically distinct geographic clades between 2008 and 2019. Additionally, we determined the jaw and belly spot pattern of a subsample of 95 individuals (22–109 cm snout-vent length). PERMANCOVA was used to investigate the relationships between head colour and spot patterns, to the caiman size, sex, and geographic lineage, as well as ambient temperature. Variation in head colour, and jaw and belly spot patterns, were related to genetic lineage, snout-vent length and temperature, but the model explained only ~45.4% of the variance in the data. Sex was not significantly related to the head colour, or jaw and belly spot patterns. Dwarf caimans inhabiting cooler climates tend to be darker than individuals from warmer areas, and individuals from the “Cerrado-Pantanal” and “Bolivia” lineages generally darker than the “Amazon” and “Madeira” lineages. However, individuals of a given size in different lineages overlap greatly in colour patterns and colour alone could not be used to distinguish lineages. The Natterer's hypothesis of head-colour as diagnose from “Cerrado-Pantanal” lineage, cannot be completely accepted according our quantitative analysis, although there are a variation in the geographic distribution of these phenotypic traits, and the “Cerrado-Pantanal” lineage had been the most distinct among the lineages.