Barcoding-inferred biodiversity of shallow-water Indo-Pacific demosponges
The Indo-Pacific is the world's largest marine biogeographic region. It is characterised by taxon-specific and different degrees of biogeographic connectivity, and harbours the majority of demosponge species currently known to science. Comparisons between several regional sponge faunas have been undertaken in the past – most based on morphological features of individual putative sponge species. The Sponge Barcoding Project (www.spongebarcoding.org), in tandem with other regional DNA taxonomy campaigns, now has provided one of the largest DNA-based taxonomic data collections from the Indo-Pacific. These data, acquired from analyses of specimens, e.g., from the Red Sea, Persian Gulf, Mayotte, Mauritius, Indonesia, Thailand, Western Australia, Queensland, and the Polynesian Islands, now provide a platform to investigate fundamental but as yet unanswered questions on the distribution, evolution, dispersal, and ecology of demosponges in the Indo-Pacific. Our data displays high levels of endemism among demosponges, consistent with other biodiversity data from twelve different Indo-Pacific marine provinces. This corroborates few case studies on sponges have mostly rejected the presence of cosmopolitan or otherwise widespread sponge species, consistent with similar hypotheses of other marine invertebrates.. High faunal overlaps are revealed between the Red Sea and the Gulf, with relatively small connectivity with other marine provinces of the Western Indian Ocean. In the Western Indian Ocean, we observe a strong faunistic boundary to the Central Indo-Pacific sponge fauna. The Polynesian sponge faunas are comparatively isolated from the Central Indo-Pacific. Further patterns and underlying processes are discussed.