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Data from: Genome scanning reveals the genetic basis of a color pattern morphotype in an island population of the European adder (Vipera berus)

Casillas, Nina1; Petersen, Bent2; Martin, Sarah1; Brealey, Jaelle3; Bieker, Vanessa1; Morin Lagos, Jaime1; Dolmen, Dag1; Madsen, Thomas4; Nielsen, Rasmus5; Allentoft, Morten6; Cerca, José1; Martin, Michael1

Published May 20, 2026 on Dryad. https://doi.org/10.5061/dryad.s1rn8pknn

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May 20, 2026 version files 3.35 GB

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Abstract

Color polymorphism is an important trait due to its role in defense strategies, feeding habits, environmental responses such as temperature regulation, and overall fitness. While the genetic basis of color polymorphism is well understood in mammals, it remains relatively understudied in non-avian reptiles. Vipera berus, the European adder, is the most widely distributed and northernmost terrestrial snake in the world. Similar to other European vipers, V. berus exhibits a range of dorsal color patterns spanning from zig-zag to complete melanism. However, a unique longitudinal dorsal stripe pattern was recently discovered in the isolated Gossa Island (~45 km²) population of Norway, where approximately 5% of snakes exhibit this distinct pattern instead of the common dorsal zig-zag pattern. In this study, we investigated the genetic basis of the unique phenotype observed on Gossa by combining low-depth whole-genome shotgun sequencing and pairwise FST genome-scanning. We discovered five regions with significant genomic differentiation, which include three associated genes, including the pre-melanosome gene (PMEL), which encodes a well-known transmembrane glycoprotein that is a key component of melanosome organelles. Our results provide insight into the evolution and genetic basis of pigmentation of squamate reptiles using the unbiased approach of genome scanning, a method that has rarely been used in this context.