Exploring ecological specialization in pipefish using genomic, morphometric and ecological evidence

Abstract Aim Theory predicts that ecological specialization should be rare in marine ecosystems, given dispersal barriers are less effective the vastness of sea compared with those terrestrial settings. This paradigm, however, hardly fits classical theories local adaptation, raising question how diversity originates a highly interconnected system. In present study, we investigated arises widely distributed species, seaweed pipefish Syngnathus schlegeli . Location Chinese coastal waters. Methods We integrated morphological (geometric morphometry), genetic (RADseq) and (species distribution models n ‐dimensional hypervolumes) evidence to shed light on population structuring S. Results revealed existence north‐to‐south phenotypic gradient eye size among populations. differentiation was paralleled by divergence, South China Sea populations emerging as relatively independent. further observed high niche northern, central southern populations, resulting from both expansion shift processes. Projected habitat suitability onto Last Glacial Maximum historical between East seas. Main conclusions showed effect this segregation, concert niche‐driven differentiation, might lead establishment three distinct clades across pipefish. Ultimately, our study demonstrates even connected environment maintains potential for specialization.