Congruence between nuclear and mitochondrial genes in Demospongiae: A new hypothesis for relationships within the G4 clade (Porifera: Demospongiae)

[Display omitted] ► Classification of Demospongiae G4 group was tested using rRNA and CO1 sequences. ► This is the most comprehensive study of the Demospongiae G4 clade. ► The LSU and CO1 genetrees conflict with the current morphological classification. ► A new hypothesis for relationships of G4 taxa is proposed. ► The order Axinellida Lévi, 1973 is resurrected and two new families are created. The current morphological classification of the Demospongiae G4 clade was tested using large subunit ribosomal RNA (LSU rRNA) sequences from 119 taxa. Fifty-three mitochondrial cytochrome oxidase 1 (CO1) barcoding sequences were also analysed to test whether the 28S phylogeny could be recovered using an independent gene. This is the largest and most comprehensive study of the Demospongiae G4 clade. The 28S and CO1 genetrees result in congruent clades but conflict with the current morphological classification. The results confirm the polyphyly of Halichondrida, Hadromerida, Dictyonellidae, Axinellidae and Poecilosclerida and show that several of the characters used in morphological classifications are homoplasious. Robust clades are clearly shown and a new hypothesis for relationships of taxa allocated to G4 is proposed.