Molecular taxonomy and phylogeny of the Geodiidae (Porifera, Demospongiae, Astrophorida) - combining phylogenetic and Linnaean classification

Cardenas, P., Rapp, H.T., Schander, C. & Tendal, O. S. (2010). Molecular taxonomy and phylogeny of the Geodiidae (Porifera, Demospongiae, Astrophorida) - combining phylogenetic and Linnaean classification.-Zoologica Scripta, 39, 89-106. According to the fossil records, the Geodiidae represents one of the oldest families of demosponges (Phylum Porifera). There are approximately 220 described extant species, geographically and bathymetrically widely distributed around the world. Species of this family all share a two-layered cortex with ball-shaped spicules called 'sterrasters' in the endocortex. However, molecular studies have questioned the monophyly of the group. Moreover, the evolutionary history and the intrafamily relationships of the Geodiidae are not fully resolved. Using a partial sequence of the cytochrome c oxidase subunit 1 (COI) gene and a partial sequence of the 28S rDNA gene (D1-D2 domains), we present the first molecular phylogeny focusing oil this group. The congruent results from the two gene fragments suggest that (i) the Geodiidae is monophyletic, (ii) the Erylinae/Geodinae subdivision sensu Sollas, 1888 is valid and that (iii) Isops and Sidonops ire junior synonyms of Geodia. The synonymization of Isops and Sidonops implies that the oscule/pore morphology as a diagnostic character should be abandoned. Geodia bentscheli nom. nov. has been given for Geodia mesotriaena (Hentschel, 1929). This study served as the basis for a revised phylogenetic classification of the Geodiidae. Well-supported clades led to the establishment of clade names following the PhyloCode. The Geodinae clade is strongly supported and notably composed of Depressiogeodia, Cydonium and Geodia. A morphological synapomorphy of Geodinae is the presence of euasters in the ectocortex. The Erylinae (Erylus, Penares, Caminus and Pachymatisma) form a strongly supported monophyletic group with three morphological synapomorphies: (i) loss of anatriaenes and protriaenes, (ii) microrhabds (or spherules) in the ectocortex and (iii) short-shafted triaenes. The Erylus monophyly is ambiguous. Erylus species are distributed in three well-supported clades. Finally, spicule homology in the cortex of the Geodiidae is discussed.