GENETIC-EVIDENCE FOR CRYPTIC SPECIATION IN ALLOPATRIC POPULATIONS OF 2 COSMOPOLITAN SPECIES OF THE CALCAREOUS SPONGE GENUS CLATHRINA

Many sponge species are considered to be cosmopolitan. However, the systematics of marine sponges are very difficult because of the paucity of taxonomically useful characters, and hence the apparently cosmopolitan nature of many species may be simply a consequence of this. In this paper, geographically distant populations of two pairs of cosmopolitan calcareous sponges of the genus Clathrina were compared genetically. C. clathrus and C. cerebrum were collected by SCUBA diving between January and March 1989 from two localities: the Mediterranean Sea at La Vesse, near Marseille, Frances, at 9 to 12 m depth, and from the South West Atlantic at Arraial do Cabo, about 200 km east of Rio de Janeiro, at 2 to 10 m depth. Very high levels of gene divergence were found between the allegedly conspecific populations. The levels of genetic identity, I, observed are so low (I = 0.128 and 0.287) that the populations clearly cannot be considered conspecific. New species names of C. aurea sp. nov. and C. brasiliensis sp. nov. are therefore assigned to the southwest Atlantic counterparts of C. clathrus and C. cerebrum, respectively. It is concluded that, at least for the species studied, and probably for many other species in taxonomically difficult groups, the actual distributions of single species may be far more geographically restricted than is generally assumed.