HOOPER, John N.A.; SOEST, Rob W.M. Van; Queensland Museum, Brisbane; Zoological Museum University of Amsterdam: Sponge biodiversity and biogeography

Even if the scope of the phylum Porifera is now better resolved, many features of sponge biodiversity are still poorly understood, including: the magnitude of species diversity, their spatial distributions, mechanisms for recruitment, dispersal and connectivity, and the contribution of historical biogeographic events to modern day spatial distributions. Approximately 7,000 �valid� morphospecies have been described worldwide, from an estimated fauna of about 15,000 extant species (although this estimate largely ignores the relatively unexplored thinly encrusting, sciaphilic communities, and the growing evidence for cryptic sibling species hiding amongst many putative morphospecies). Fundamental sponge bauplans have remained largely unchanged since the Late Cambrian (509MYA), and despite several major extinction events in the interim, they have radiated and diversified in all Recent seas. This evolutionary success may be due to their huge capacity to adapt and survive in marginal life situations (perhaps through their unique possession of highly mobile cells that confer plasticity in growth form), that has enabled sponges to colonise and evolve in all aquatic habitats � from ephemeral (quasi-terrestrial) ones to the more stable marine abyssal zones. A number of sponge biodiversity �hotspots� can been seen today, based on their significant contributions to benthic biomass (e.g. Caribbean faunas), primary productivity (e.g. shallow coral reef faunas), high species diversity (e.g. Indo-Malay archipelago), and/or very high endemism (e.g. Gondwanan fauna). Patterns of modern day sponge distributions are compared with other sessile invertebrate taxa, and underpinning contributory mechanisms are considered (historical biogeography, dispersal and connectivity (including larval behaviour, longevity, fragmentation and epigenetic inheritance), and the concept of cosmopolitanism.