Robert W. Thacker

Interim Chair      
Professor, Ecology and Systematics


(205) 934-4006
(Ph.D. (Biology), 1995, University of Michigan, Ann Arbor

Research Description:

Research in my laboratory focuses on taxonomy, systematics, and the evolution of ecological interactions. Recent projects have used sponges and their symbiotic microbial communities as model systems to study coevolution among hosts and symbionts, the evolution of community structure, and the evolution of mutualistic interactions. We have found that microbial symbionts can form half of the biomass of many marine sponges, while photosynthetic symbionts can supply up to 80% of a sponge's energetic needs. Because symbiotic cyanobacteria are closely related to free-living species, I also investigate the ecology and evolution of marine and freshwater cyanobacteria. Applications of this research include collaborations with Conservation International to survey and protect the coral reef communities of Saba Bank, Netherlands Antilles, and collaborations with the Birmingham Water Works Board to examine the microbial biodiversity of a novel drinking water filtration system.

Taxonomy and systematics build the foundation for studying relationships among organisms and provide the phylogenetic context required by comparative studies and conservation biology. Despite recent revisions of the morphological classification of sponges, the taxonomy of many sponge orders remains problematic. The Porifera Tree of Life ( project is constructing a definitive phylogeny of sponges, funded by the National Science Foundation’s Assembling the Tree of Life program. We are integrating morphological and molecular approaches to systematics across the immense biodiversity represented by the four classes of sponges.

Two new projects build on the Porifera Tree of Life by developing bioinformatic tools that can be applied to all taxonomic groups. Arbor: Comparative Analysis Workflows for the Tree of Life is a novel software package for comparative evolutionary analyses. Our software is designed to place tree-thinking tools into the hands of scientists across multiple disciplines, enabling rapid advances in integrative and comparative biology at multiple phylogenetic and spatiotemporal scales. Next Generation Phenomics for the Tree of Life combines text mining, image analysis, and machine learning software to automate phenotypic character discovery and scoring from publications and images.

Representative Publications:

Shirey TB, Thacker RW, Olson JB. 2012. Composition and stability of bacterial communities associated with granular activated carbon and anthracite filters in a pilot scale municipal drinking water treatment facility. Journal of Water and Health 10(2): 244-255.

Thacker RW, Freeman CJ. 2012. Sponge-microbe symbioses: Recent advances and new directions. Advances in Marine Biology 62: 57-111.

Gochfeld DJ, Easson CG, Freeman CJ, Thacker RW, Olson JB. 2012. Disease and nutrient enrichment as potential stressors on the Caribbean sponge Aplysina cauliformis and its bacterial symbionts. Marine Ecology Progress Series 456: 101-111.

Gochfeld DJ, Kamel HN, Olson JB, Thacker RW. 2012. Trade-offs in defensive metabolite production but not ecological function in healthy and diseased sponges. Journal of Chemical Ecology 38: 451-462.

Erwin PM, Olson JB, Thacker RW. 2011. Phylogenetic diversity, host-specificity, and community profiling of sponge-associated bacteria in the northern Gulf of Mexico. PLoS ONE 6(11): e26806.

Freeman CJ, Thacker RW. 2011. Complex interactions between marine sponges and their symbiotic microbial communities. Limnology and Oceanography 56(5): 1577-1586. doi:10.4319/lo.2011.56.5.1577

Thacker RW, Diaz MC, de Voogd NJ, van Soest RWM, Freeman CJ, Mobley AS, LaPietra J, Cope K, McKenna S. 2010. Assessment of sponge biodiversity on Saba Bank, Netherlands Antilles. PLoS ONE 5(5): e9622.

Sharp K, Arthur KE, Gu L, Ross C, Harrison G, Gunasekera SP, Meickle T, Matthew S, Luesch H, Thacker RW, Sherman DH, Paul VJ. 2009. Phylogenetic and chemical diversity of three chemotypes of bloom-forming Lyngbya species (Cyanobacteria: Oscillatoriales) from reefs of Southeastern Florida. Applied and Environmental Microbiology 75(9): 2879-2888.

Slattery M, Kamel HN, Ankisetty S, Gochfeld DJ, Hoover CA, Thacker RW. 2008. Hybrid vigor in a tropical Pacific soft coral community. Ecological Monographs 78(3): 423-443.

Erwin PM, Thacker RW. 2008. Cryptic diversity of the symbiotic cyanobacterium Synechococcus spongiarum among sponge hosts. Molecular Ecology 17: 2937-2947.

Erwin PM, Thacker RW. 2008. Phototrophic nutrition and symbiont diversity of two Caribbean sponge-cyanobacteria symbioses. Marine Ecology Progress Series 362: 139-147.

Taylor MW, Thacker RW, Hentschel U. 2007. Evolutionary insights from sponges. Science 316: 1854-1855.

Erwin PM, Thacker RW. 2007. Incidence and identity of photosynthetic symbionts in Caribbean coral reef sponge communities. Journal of the Marine Biological Association of the United Kingdom 87: 1683-1692.

Erwin PM, Thacker RW. 2007. Phylogenetic analyses of marine sponges within the order Verongida: a comparison of morphological and molecular data. Invertebrate Biology 126(3): 220-234.