title: Ribosomal ITS sequences allow resolution of freshwater sponge phylogeny with alignments guided by secondary structure prediction.
abstract: Freshwater sponges include six extant families which belong to the suborder Spongillina (Porifera). The taxonomy of freshwater sponges is problematic and their phylogeny and evolution are not well understood. Sequences of the ribosomal internal transcribed spacers (ITS1 and ITS2) of 11 species from the family Lubomirskiidae, 13 species from the family Spongillidae, and 1 species from the family Potamolepidae were obtained to study the phylogenetic relationships between endemic and cosmopolitan freshwater sponges and the evolution of sponges in Lake Baikal. The present study is the first one where ITS1 sequences were successfully aligned using verified secondary structure models and, in combination with ITS2, used to infer relationships between the freshwater sponges. Phylogenetic trees inferred using maximum likelihood, neighbor-joining, and parsimony methods and Bayesian inference revealed that the endemic family Lubomirskiidae was monophyletic. Our results do not support the monophyly of Spongillidae because Lubomirskiidae formed a robust clade with E. muelleri, and Trochospongilla latouchiana formed a robust clade with the outgroup Echinospongilla brichardi (Potamolepidae). Within the cosmopolitan family Spongillidae the genera Radiospongilla and Eunapius were found to be monophyletic, while Ephydatia muelleri was basal to the family Lubomirskiidae. The genetic distances between Lubomirskiidae species being much lower than those between Spongillidae species are indicative of their relatively recent radiation from a common ancestor. These results indicated that rDNA spacers sequences can be useful in the study of phylogenetic relationships of and the identification of species of freshwater sponges.
authors.affiliation: Laboratory of Analytical Bio-Organic Chemistry, Limnological Institute of the Siberian Branch of the Russian Academy of Sciences, Ulan-Batorskaya 3, 664 033 Irkutsk, Russia. vitskovich@yahoo.com
authors.forename: Valeria
authors.initials: V
authors.lastname: Itskovich
authors.forename: Andrey
authors.initials: A
authors.lastname: Gontcharov
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Masuda
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nohno
authors.forename: Sergey
authors.initials: S
authors.lastname: Belikov
authors.forename: Sofia
authors.initials: S
authors.lastname: Efremova
authors.forename: Martin
authors.initials: M
authors.lastname: Meixner
authors.forename: Dorte
authors.initials: D
authors.lastname: Janussen
mesh_terms: D000818:Animals; D001483:Base Sequence; D005618:Fresh Water; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D011161:Porifera / Q000235:genetics*; D012270:Ribosomes / Q000235:genetics*; D016415:Sequence Alignment; D014158:Transcription, Genetic / Q000235:genetics*