Morphology and molecules on opposite sides of the diversity gradient: Four cryptic species of the Cliona celata (Porifera, Demospongiae) complex in South America revealed by mitochondrial and nuclear markers

► Four clades found within South American Cliona celata species complex. ► Broad discontinuous distribution in the Atlantic Ocean for one clade. ► High gene flow between Atlantic and Pacific coasts for one clade. ► Spicule morphology not suitable to distinguish among clades. ► Each clade correspond to different species, not differentiated by morphology.