Meeting Abstract

28.10  Jan. 5  Evolutionary Specialization of Sponge-Cyanobacteria Symbioses: Cospeciation vs. Colonization THACKER, R.W.; Univ. of Alabama at Birmingham thacker@uab.edu

Highly specific interactions between hosts and symbionts are often attributed to cospeciation; however, independent colonization events can generate similar patterns of host specificity. Symbiotic filamentous cyanobacteria (Oscillatoria spongeliae) have been reported from diverse marine sponges, with each sponge species hosting a unique clade of cyanobacteria. Initial phylogenetic analyses of Indo-Pacific sponges in the order Dictyoceratida supported the hypothesis of cospeciation between sponges and their symbiotic filamentous cyanobacteria. More recent investigations have examined the 16S ribosomal RNA gene sequences of filamentous cyanobacteria associated with three Caribbean sponges, including Hyrtios violaceus (Dictyoceratida) from Belize and two newly described species in the order Haplosclerida from the Bocas del Toro region of Panama, Haliclona n. sp. and Xestospongia n. sp. The addition of these three species to previous phylogenies reveals the presence of two major clades of O. spongeliae, with each clade represented in the Indo-Pacific and Caribbean regions. Although evidence for cospeciation can be found within sponge genera, the revised phylogenies suggest multiple independent colonization events among sponge genera. O. spongeliae appears to have initially colonized a dictyoceratid host, spreading to other species by a combination of cospeciation and colonization events, with independent colonizations of two haplosclerid hosts.