REPORT A case for redefining the boundaries of the Mesoamerican Reef Ecoregion Iliana Chollett 1,2 • Lysel Garavelli 3 • Daniel Holstein 4 • Laurent Cherubin 3 • Stuart Fulton 5 • Stephen J. Box 1,6 Received: 6 January 2017 / Accepted: 24 May 2017 Ó Springer-Verlag Berlin Heidelberg 2017 Abstract The Mesoamerican Reef (MAR) is an intercon- nected system that supports the local economies of four countries through the provision of seafood and tourism. Considerable financial, research and management effort has been invested in this priority ecoregion, whose boundaries were defined more than 18 yr ago based on best available data on oceanographic patterns, reef and water- shed distribution. The long-term persistence of the MAR depends, however, on ensuring that all of its constituent parts are appropriately managed, and the current bound- aries may not respond to this need. Here we assess the suitability of the current boundaries of the MAR using information on physical environments and larval connec- tivity of three key species. Our research indicates the boundaries of the ecoregion require an adjustment, as the exclusion of key areas in eastern Honduras might jeopar- dize the persistence of the entire network of connected reefs, and areas in northern Yucatan belong to a different environmental regime and may require different manage- ment strategies. Keywords Caribbean Á Connectivity Á Oceanography Á Biogeography Á Tropical coastal ecosystems Introduction The Mesoamerican Reef (MAR) is an interconnected sys- tem of coastal habitats which constitutes a priority region for conservation in the world (Olson and Dinerstein 2002; Fig. 1). The MAR is the longest barrier reef system in the western hemisphere and the second longest in the world, extending over one thousand kilometres along the coastli- nes of Mexico, Belize, Guatemala and Honduras. The region is a biodiversity and cultural hotspot (Roberts et al. 2002) and has great ecological, aesthetic, cultural and economic value, sustaining nearly two million people from the four countries (FAO 2000). Identifying the boundaries of the ecoregion was one of the first steps to start coordinated conservation efforts in the MAR. Collective work in the region started with the Tulum Declaration during the first International Year of the Reef in 1997. At this time, the governments of Mexico, Belize, Guatemala and Honduras committed to work together to promote the conservation and sustainable use of their shared resource. The declaration catalysed the work of several non-governmental and governmental organizations that produced a conservation blueprint for the region and delineated the limits of the ecoregion (Kramer and Kramer 2002). Since then, the MAR has become an international conservation priority ecoregion (Olson and Dinerstein 2002), stimulating targeted research, monitoring and management. Communicated by Ecology Editor Dr. Alastair Harborne & Iliana Chollett iliana.chollett@gmail.com 1 Smithsonian Marine Station, Smithsonian Institution, Fort Pierce, FL 34949, USA 2 Coastal and Marine Sciences Institute, University of California Davis, Davis, CA 95616, USA 3 Florida Atlantic University, Harbor Branch Oceanographic Institute, Fort Pierce, FL 4946, USA 4 Nicholas School of the Environment and Duke Marine Lab, Duke University, Beaufort, NC 28516, USA 5 Comunidad y Biodiversidad A.C, Puerto Morelos, Quintana Roo, Mexico 6 Present Address: Rare, Arlington, VA 22201, USA 123 Coral Reefs DOI 10.1007/s00338-017-1595-4