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Biogeography and metapopulation genetics of understudied hydrozoan reef foundation species Millepora spp.

Final Report Summary - HYDROREEF (Biogeography and metapopulation genetics of understudied hydrozoan reef foundation species Millepora spp.)

Reef ecosystems are one of the most threatened environments on Earth. Because they provide invaluable services to coastal communities and sustain a large part of global biodiversity, the conservation of their biodiversity and functioning is vital. Millepora species are the second reef builders after scleractinians, yet little is known about them. Such foundation species, providing shelter, food and nurseries to thousands of species are essential to protect. The project “HydroReef” aims to characterize biodiversity and metapopulation dynamics of millepores through a multidisciplinary approach involving DNA barcoding, phylogeny, comparative phylogeography and population genetics on various spatio-temporal scales. First, the DNA barcoding part helped accurately assessing biodiversity in this problematic group and revealed cryptic species in the Red Sea and the South western Indian Ocean, pinpointing areas of evolutionary importance. The connectivity levels of Millepora platyphylla populations revealed barriers to gene flow over the Indo-Pacific distribution and is suggesting several distinct units for conservation. The genetic diversity of Millepora platyphylla further helped to understand the Indo-Pacific gradient of biodiversity, with central Pacific populations showing depauperate genetic diversity, west Pacific population highly diversified and West Indian Ocean populations being intermediate; suggesting complex dispersal dynamics. Fine scale population genetics using microsatellite markers provided estimates of ecological connectivity (DNA tracking of dispersal by parentage analyses). The respective proportion of asexual and sexual reproductions on space pre-emption and population persistence was uncovered by studying more than 3500 colonies in Moorea, French Polynesia. Clonal reproduction was dominant in Moorea and clonal lineages displaying distinct morphotypes in distinct environments revealed phenotypic plasticity in fire corals. Overall, these results will provide information directly enhancing the protection and restoration of coral reefs. It will reveal regions of evolutionary importance and the spatial dimension of millepore connectivity, crucial information for both global scale conservation and design of Marine Protected Areas.