Modelling dispersal and connectivity of broadcast spawning corals at the global scale

Abstract Aim We develop the first global model of connectivity for a generic broadcast spawning coral, and compare the results to connectivity estimates from genetic studies, general biogeographic patterns and theories. We also derive various ‘connectivity indices’ describing relative isolation and source potential between locations. Location Modelled oceans 47° S –47° N . Methods Dispersal of model coral ‘larvae’ was simulated over 8 years using an individual‐based biophysical dispersal model driven by 1/12°‐resolution surface ocean current data and incorporating individual trait variability (e.g. a phased pre‐competency period). Source and arrival locations of modelled larvae on suitable reef habitat gave standardized dispersal paths and relative levels of connectivity. Results In the model c . 50% of connections occurred within 50–100 km, with rarer dispersal between regions linking entire oceans in a ‘stepping stone’ fashion. The central P acific was an almost complete barrier to dispersal, only rarely breached westward from the G alapagos to M arquesas I slands. Areas showing strong isolation also included H awaii, E aster I sland, the R ed S ea and the eastern A tlantic. The I ndo‐ W est P acific and G reat B arrier R eef showed the highest levels of connectivity, with secondary peaks in the western I ndian O cean, corresponding to areas of enriched coral diversity. The central I ndo‐ P acific diversity hotspot was overall a greater source than sink for dispersal. Conclusions This study provides a global view of connectivity that complements genetic and biogeographic work as well as providing a number of novel findings relevant to biogeographic theories (e.g. the central I ndo‐ P acific as a dispersal source; J ohnston A toll as the sole ‘stepping‐stone’ into H awaii). Discrepancies with proposed connectivity patterns (e.g. one‐way, westward, connectivity across the central P acific) present hypotheses for future research. The model represents an effective tool for exploring the factors controlling connectivity on this scale and the effects of climate change on future connectivity, and will also aid predictions of future reef distributions.