Sponge taxonomy in the -omics era: resolving Haplosclerida polytomies with phylogenetics and metabolomics

Abstract

With several new taxa described every day, we are still in the Age of Discovery of the biodiversity. On the other hand, the sixth mass extinction of biological species is underway, rapid, and aggressive, which renders the description of biodiversity to inform conservation, of high priority. Systematics allows a reliable assessment of biological diversity, facilitating conservation management. Unfortunately, marine invertebrates often present few morphological characters that help to define boundaries and classify taxa. Therefore, the integration of new approaches and data is necessary to obtain more robust diagnostic characters enabling a more accurate identification of the taxa. The sponge order Haplosclerida is no exception within the Metazoa in general when it comes to a sizeable mismatch between the growing phylogeny of the group and its accepted classification. The monophyly of marine haplosclerids is well supported, whereas many of the Haplosclerida families and even genera are paraphyletic. A deep morphological, molecular and metabolomic investigation of all species of the genus Arenosclera (Callyspongiidae, Haplosclerida) allowed a reassessment of the genus’ diagnosis, a description of the new genus Arenospicula gen. nov., and a reorganization of species in the classification. Our results highlight the potential of an integrative approach to solve part of the extensive mismatch between phylogeny and classification for the Haplosclerida. Integration of morphology, molecular and metabolomic data is a robust way to face the challenge of widespread polyphyly in every non-monotypic higher taxon within the Haplosclerida. Integration of these data could also lead to a more accurate and natural view of genera and family boundaries of currently para- and polyphyletic taxa in marine invertebrates.