Having the balls to colonize - The Ephydatia fluviatilis group and the origin of (ancient) Lake "endemic" sponge lineages

Spongillida (freshwater sponges) constitute an integral part of the world's lacustrine ecosystems. Their radiation and worldwide distribution into nearly every freshwater habitat is predominantly facilitated by the formation of so-called gemmules, i.e., globular endurance and propagation stages. Widespread species produce gemmules in a wide array of morphs, while in (ancient) lake endemic lineages gemmules are absent. Contrary to current classification, earlier molecular studies on non-type material indicated that gemmule-lacking lineages are unrelated, and endemic taxa were derived from a cosmopolitan (and paraphyletic) founder lineage. In this study we investigate this hypothesis with type material, particularly focussing on endemic taxa potentially derived from common ancestor shared with the widespread Ephydatia fluviatilis. We demonstrate that taxa regarded as endemic from Lake Ohrid (Ochridaspongia), Lake Kinneret/Tiberias (Cortispongilla) and Lake Titicaca (Balliviaspongia) are derived from the founder lineage, but unrelated to other, particularly Afrotropical, ancient lake sponges, and discuss implications for understanding freshwater sponge phylogeny and evolution.