2.2 Parameters
We also searched the scientific literature to find a possible link between the colour variation in populations and a possible cause of their frequency, such as a selective advantage, population bottleneck, or heterozygote deficiency. Because the latter is merely speculative, we also tried to retrieve genetic data from the same population. In total, we noted for each colour variant: the type (e.g. dilution, melanism, leucism), geographic location, speculated cause, gene mutation, frequency, allelic richness (AR), observed (HO) and expected (HE) heterozygosity, and inbreeding coefficient (FIS), when such data was available. All genetic papers were based on microsatellites, with a minimum of 5 loci. When FIS values could be retrieved, we compared these to the body size, population size, and level of habitat fragmentation in the area where the colour variable population occurs, to draw potential correlations. Because exact population sizes are often difficult to retrieve, they were divided into categories (< 50, < 250, < 1000, > 1000 adult individuals), derived from literature. The level of habitat fragmentation was divided into categories (high, medium, low) based on metrics provided by Crooks et al. (2017).