REPORT Genetic assessment of connectivity in the common reef sponge, Callyspongia vaginalis (Demospongiae: Haplosclerida) reveals high population structure along the Florida reef tract M. B. DeBiasse • V. P. Richards • M. S. Shivji Received: 7 June 2009 / Accepted: 28 September 2009 / Published online: 25 October 2009 Ó Springer-Verlag 2009 Abstract The genetic population structure of the com- mon branching vase sponge, Callyspongia vaginalis, was determined along the entire length (465 km) of the Florida reef system from Palm Beach to the Dry Tortugas based on sequences of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene. Populations of C. vaginalis were highly structured (overall U ST = 0.33), in some cases over distances as small as tens of kilometers. However, non- significant pairwise U ST values were also found between a few relatively distant sampling sites suggesting that some long distance larval dispersal may occur via ocean currents or transport in sponge fragments along continuous, shallow coastlines. Indeed, sufficient gene flow appears to occur along the Florida reef tract to obscure a signal of isolation by distance, but not to homogenize COI haplotype fre- quencies. The strong genetic differentiation among most of the sampling locations suggests that recruitment in this species is largely local source-driven, pointing to the importance of further elucidating general connectivity patterns along the Florida reef tract to guide the spatial scale of management efforts. Keywords Porifera Á Coral reef connectivity Á Genetic diversity Á Dispersal Á Cytochrome c oxidase subunit one (COI) Introduction An often recommended and implemented strategy for reducing and reversing coral reef degradation is the establishment of marine protected/reserve areas (MPAs). An important criterion to inform the design and assess the effectiveness of MPAs is the level of demographic con- nection within and among coral reef sections (Palumbi 2003; Almany et al. 2009; Planes et al. 2009). The east coast of Florida, USA, is a densely populated and devel- oped region that also contains the majority of continental US coral reefs, much of it in an advanced state of impairment (Causey et al. 2002; Pandolfi et al. 2005). Less than 5% of Florida’s reefs are currently protected under a no-take MPA designation, and there are increasing calls to strategically expand these areas to reduce continued threats to reef health (Pandolfi et al. 2005). Despite the considerable ecosystem value and impor- tance of the Florida coral reef tract as a socioeconomic resource (Causey 2008), there has been surprisingly little assessment of the detailed dynamics of connectivity within this degrading ecosystem. Since many biological and physical factors influence connectivity patterns among coral reefs (Galindo et al. 2006; Taylor and Hellberg 2006; Underwood et al. 2007), deriving a general picture of connectivity to inform conservation and management efforts will require information from diverse species dis- playing various life history strategies. Previous work examining detailed connectivity patterns among multiple sampling sites within the Florida reef tract has Communicated by Biology Editor Dr. Ruth Gates M. B. DeBiasse Á V. P. Richards Á M. S. Shivji (&) National Coral Reef Institute, Oceanographic Center, Nova Southeastern University, 8000 North Ocean Drive, Dania Beach, FL 33004, USA e-mail: Mahmood@nova.edu Present Address: M. B. DeBiasse 107 Life Sciences Building, Louisiana State University, Baton Rouge, LA 70803, USA 123 Coral Reefs (2010) 29:47–55 DOI 10.1007/s00338-009-0554-0