Aquatic Ecology & Evolution

Speciation and adaptive radiation

Genomics of ecological polymorphism in a marine fish group

mediterranean wrasse by Ole Seehausen

Marine fish were long thought of as not doing geographically localized adaptive radiations. However, the geologically young Mediterranean Sea does host several small to moderately sized species radiations. One of them occurs in the European wrasses (Labrinae) with some 15 species in two largely endemic clades. Many of the species in both clades share a very remarkable phenotypic polymorphism with brown morphs that tend to live among rocks, and green morphs that are strictly associated with Posidonia seagrass.

Little is known about the genetic mechanism that permits such remarkable polymorphism in full sympatry. The polymorphism may be due to phenotypic plasticity or developmental plasticity, may have a simple Mendelian genetic basis, or more complicated mechanisms could be at work, including speciation. We are investigating this polymorphism, using next generation sequencing to test for genetic differences between morphs.

Eco-genomics in marine fish team