Meeting Abstract

S8-1.5  Sunday, Jan. 6  Calcarea evolution: morphology and molecules KLAUTAU, M.*; AZEVEDO, F.; CóNDOR LUJáN, B.; RUSSO, C.A.M.; COLLINS, A.; Universidade Federal do Rio de Janeiro; Smithsonian National Museum of Natural History

One great challenge for taxonomists is how to integrate morphological and molecular data, especially for groups with few morphological characters and virtually no fossil record. One example is the class Calcarea. Whilst the silicious sponges may present hundreds of spicule types, calcareans have only four main types of calcium carbonate spicules, which are used for phylogenetic affiliation, but it remains to be tested whether those characters have a phylogenetic signature. Calcarean subclasses Calcinea and Calcaronea are clearly monophyletic by a wide variety of characters and molecular data have consistently agreed with this split. For other taxonomic levels, however, monophyly was not found. Recent analysis of the paraphyletic genus Clathrina showed the presence of phylogenetic signal in the skeleton, so it remains to be seen if those results apply to other calcinean groups. In this study, we have analysed 5.8S, 18S, 28S and the ITS1 and ITS2. Interestingly, many other Clathrina species included here have reinforced conclusions that Clathrina is not a monophyletic genus and that spicule composition has a strong phylogenetic signal. True members of Clathrina are clathroid, with a skeleton without tetractines. A new genus is characterised by the presence of a well-defined clathroid body with triactines, tripods and tetractines with spines. Moreover, clathrinas with tetractines as the main spicule group should be classified as Ascandra. Leucetta groups with Pericharax, Leucaltis and Leucettusa. Species of these genera have a cortex with large spicules and also very small triactines and/or tetractines in the atrium and choanosome. Our results reinforce that the skeleton in calcareous sponges may show a very strong phylogenetic signal and suggest that calcarean phylogenetics is best addressed using large numbers of species of few genera.