DNA reconciles morphology and colouration in the drunk blenny genusScartichthys(Teleostei: Blenniidae) and provides insights into their evolutionary history

The blenniids of the genusScartichthysare one of the most common fishes of Central and South American Pacific coastal reefs. This being said, Scartichthys spp. remain difficult to identify in the field, and identification is particularly challenging across the ca. 6000 km where three of the four currently accepted species are known to occur in sympatry. A reason for this is that the main taxonomic characters from traditional taxonomy are indeed elusive. Additionally, At the same time, species can display multiple colour patterns in the field, depending on their ontogenetic stage, habitat association, and reproductive behaviour. Overall, molecular characterization is warranted to help address these issues. Here, we have used a novel approach to revise the genus by combining colouration, morphological, and molecular data of representative specimens of the four currently valid species and seven described colour patterns. From this, we show that only three of the four species should be considered as valid;Scartichthys gigas(Steindachner, 1876),S. variolatus(Valenciennes, 1836), andS. viridis(Valenciennes, 1836); while S. crapulatus Williams 1990 should be synonymized withS. viridis. In the same way, our analyses show that one of the colour patterns attributed so far only toS. gigasis characteristic of the juvenile stages ofS. viridis. Our time-calibrated phylogeny shows that this genus is relatively young and that the estimated time of divergence betweenScartichthys gigasandS. viridisis around 1.71 Ma. In comparison, the Desventuradas and Juan Fernandez Islands endemicS. variolatusdiverged about 1.95 Ma. Our results help to clarify the taxonomy of Scartichthys.