Molecular and morphological assessment of tropical sponges in the subfamily Phyllospongiinae, with the descriptions of two new species

Sponges in the subfamily Phyllospongiinae are important components of coral reefs. However, significant taxonomic inconsistencies exist in this group due to the lack of useful morphological characters for species delineation. This study assesses the systematics of some common phyllospongiinids in the genera Carteriospongia, Phyllospongia and Strepsichordaia from tropical Australia and the Red Sea, by using a multigene approach that utilizes the Internal Transcribed Spacer 2, the complete ribosomal 18S rRNA and three 28s rRNA gene regions (D1 D2, D3 D5 and D6D8), which produced a phylogenetic framework in which complementary morphological taxonomic assessments were performed. Type specimens were included, where available, and six species clades were recovered, including the well-established Phyllospongia papyracea and Strepsichordaia lendenfeldi. Carteriospongia foliascens, the type species for the genus Carteriospongia, is transferred to the genus Phyllospongia, resulting in Carteriospongia becoming a synonym of Phyllospongia. Consequently, Carteriospongia flabellifera is removed from Carteriospongia and is reinstated to its original designation of Polyfibrospongia flabellifera. Two new species, Phyllospongia bergquistae sp. nov. and Polyfibrospongia kulit sp. nov., are described. With phyllospongiinid sponges increasingly used as models for assessing the effects of climate change and anthropogenic stressors, this study provides a reliable systematics framework for the accurate identification of common phyllospongiinids across the Indo-Pacific.