Aim We evaluated underlying mechanisms and genetic effects of climatedriven range expansion of Rhizophora mangle L., a coastal foundation species, along both West (WFL) and East (EFL) Florida, USA.Location Eight sites encompassing the entire Florida R. mangle range at a regional scale.Methods We characterized R. mangle population genetic structure with a combination of genetic analyses using seven microsatellite loci and modelbased propagule transport. We tested hypotheses on the genetic effects of range expansion along both WFL and EFL. Finally, we compared WFL and EFL range edges and assessed potential factors shaping observed differences.Results Regional-scale Florida R. mangle genetic structure is shaped in part by the non-independent effects of geographical distance and ocean currents that drive asymmetric propagule transport from WFL to EFL. WFL conformed to theoretical expectations of range expansion, with pronounced divergence at the range edge, whereas EFL deviated from expectations. Significant differences in diversity and differentiation at the WFL and EFL range edges were attributed to differences in migration rates, population size and founder effects.Main conclusions Contrasting genetic landscapes at the WFL and EFL range edges are in part the product of variation in ocean circulation and demographic history. These underlying mechanisms may have potential ecological and evolutionary consequences that need to be addressed with further empirical research.

Marine renewable energy (MRE) harnesses energy from the ocean and provides a low-carbon sustainable energy source for national grids and remote uses. The international MRE industry is in the early stages of development, focused largely on tidal and riverine turbines, and wave energy converters (WECs), to harness energy from tides, rivers, and waves, respectively. Although MRE supports climate change mitigation, there are concerns that MRE devices and systems could affect portions of the marine and river environments. The greatest concern for tidal and river turbines is the potential for animals to be injured or killed by collision with rotating blades. Other risks associated with MRE device operation include the potential for turbines and WECs to cause disruption from underwater noise emissions, generation of electromagnetic fields, changes in benthic and pelagic habitats, changes in oceanographic processes, and entanglement of large marine animals. The accumulated knowledge of interactions of MRE devices with animals and habitats to date is summarized here, along with a discussion of preferred management methods for encouraging MRE development in an environmentally responsible manner. As there are few devices in the water, understanding is gained largely from examining one to three MRE devices. This information indicates that there will be no significant effects on marine animals and habitats due to underwater noise from MRE devices or emissions of electromagnetic fields from cables, nor changes in benthic and pelagic habitats, or oceanographic systems. Ongoing research to understand potential collision risk of animals with turbine blades still shows significant uncertainty. There has been no significant field research undertaken on entanglement of large animals with mooring lines and cables associated with MRE devices.

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