The Blue Frogs Project: Leveraging Community Science Data to Document Axanthism Hotspots Across the Globe

Sometimes individuals display coloration that is not typical of their species including increased dark pigmentation (melanism) or reduced pigmentation (albinism). Atypical colorations also can occur across the color spectrum in organisms that use a greater diversity of pigments to color their tissues. For instance, many frogs are green, which is usually produced through the combination of a yellow pigment and structural blue coloration. Changes in diet or genetic mutations can reduce the amount of yellow pigment in skin such that a normally green frog appears blue (axanthic). The presence of axanthism in wild populations of frogs has been documented in a handful of species in the scientific literature, but records remain rare. Thus, relative to albinism and melanism, the underlying causes and resulting consequences of axanthism are poorly understood. We leveraged the popular community science platform iNaturalist to screen hundreds of thousands of frog photographs taken by thousands of professional scientists and nature enthusiasts on six continents. To date, we have identified over 300 records of axanthism in 36 species across the frog tree of life by leveraging iNaturalist observations. Combined with records reported in the scientific literature, these data provide a first look at the spatial, phylogenetic, and temporal prevalence of axanthism in frogs and highlight focal lineages and regions for future evolutionary and ecological studies.