Molecular phylogenies challenge the classification of Polymastiidae (Porifera, Demospongiae) based on morphology

Abstract

Polymastiidae Gray, 1867 is a worldwide distributed sponge family, which has a great significance for understanding of the demosponge deep phylogeny since the former order Hadromerida Topsent, 1894 has been recently split based on the molecular evidence and a new separate order has been established for the polymastiids. However, molecular data obtained from Polymastiidae so far are scarce, while the phylogenetic reconstruction based on morphology has faced a deficit of characters along with the vagueness of their states. The present study is a phylogenetic reconstruction of Polymastiidae based on novel data on two molecular markers, cytochrome oxidase subunit I and large subunit ribosomal DNA, obtained from a broad set of species. Monophyly of the family and nonmonophyly of four polymastiid genera are revealed, suggesting a high level of homoplasy of morphological characters, which are therefore not an appropriate base for the natural classification of Polymastiidae. Although the presented phylogenies cannot yet provide an alternative classification scheme, several strongly supported clades, which may be used as reference points in future classification, are recovered and three taxonomic actions are proposed: transfer of one species from Radiella to Polymastia Bowerbank, 1862; transfer of three species from Radiella Schmidt, 1870 to Spinularia Gray, 1867; and the consequent abandonment of Radiella.

Polymastiidae (Porifera: Demospongiae) of the Nordic and Siberian Seas

“…A fringe of extra-long monactines may be present at the edge of the body. discussion Polymastia Bowerbank, 1862, with its currently accepted assortment of species , is not monophyletic as was suggested by Plotkin et al (2012) based on morphological data and confirmed by Plotkin et al (2016b) based on the CO1 and 28S rDNA phylogenies (see also Figure 1, this study). In both phylogenies the type species of Polymastia, P. mamillaris (Müller, 1806), formed a strongly supported clade with only five other species of this genus, P. andrica de Laubenfels, 1949, P. arctica (Merejkowsky, 1878), P. grimaldii (Topsent, 1913), P.…”

“…Apomorphies in 28S rDNA were defined only within the unambiguously aligned parts of the matrix (positions 1 -449, 492 -577, 585 -667, 685 -940 and 949 -2155 in the alignment). Based on the phylogenies recovered by Plotkin et al (2016b) we accept the abandonment of Radiella Schmidt, 1870. However, we stick to the traditional taxonomy of other genera even, if they are not monophyletic in these phylogenies, until a new classification of Polymastiidae is built.…”

“…However, we stick to the traditional taxonomy of other genera even, if they are not monophyletic in these phylogenies, until a new classification of Polymastiidae is built. Plotkin et al (2016b). Complete 28S rDNA alignment is used.…”

“…The species from the Nordic and Siberian Seas are highlighted. The following species from Plotkin et al (2016b) are renamed according to the classification accepted in the present study: Polymastia sp. 1 as Polymastia svenseni, Radiella hemisphaerica as Polymastia hemisphaerica, Radiella sarsii as Spinularia sarsii, Radiella sp.…”

“…In both CO1 and 28S rDNA phylogenies Polymastia boletiformis is the sister to morphologically quite distinct Quasillina brevis (Bowerbank, 1866) (Plotkin et al, 2016b Topsent, 1900;Borojevic, 1967;Cabioch, 1968;Boury-Esnault, 1987). Mediterranean polymastiidae of the nordic and siberian seas 11 (1933) relegated the former to a synonym of the latter, and this was followed by most of the later authors (e.g.…”