ИСТИНА

The Pleurobranchomorpha (Pleurobranchoidea) are a widespread clade of marine slugs and internally shelled snails that currently include two families, Pleurobranchaeidae and Pleurobranchidae. Some early branches diverged in Antarctica, but more recent clades are particularly diverse in shallow temperate and tropical waters (Martynov and Schrödl 2009; Göbbeler and Klussmann-Kolb, 2010). While the family Pleurobranchidae includes seven genera, comprising about 79 species, the family Pleurobranchaeidae includes only three genera, two of them monospecific (Bouchet and Rocroi, 2005; WoRMS, 2015). In spite of considerable morphological, anatomical and molecular work on this group, the phylogenetic placement, composition, and ranking of taxa within Pleurobranchomorpha remains uncertain. Molecular data of 17 species belonging to seven genera were included into a multi-locus phylogenetic analysis by Göbbeler and Klussmann-Kolb (2010). Four gene fragments (two nuclear, two mitochondrial) were obtained for 13 of the species. Surprisingly, the supposedly pleurobranchaeid Euselenops, without mitochondrial data available, clustered within pleurobranchids. In this work, phylogenetic relationships were inferred by analysing partial sequences of up to five mitochondrial and nuclear markers (H3, COI, 16S, 18S, 28S) of 30 species, covering all Pleurobranchomorpha genera. For the first time, sequences of the particularly interesting, northern hemispherical cold water taxa Boreoberthella and Pleurobranchella were generated. Some previously missing markers of Euselenops and other taxa of both families were supplemented. Single gene and species trees were inferred using maximum likelihood. The performance of several independent approaches of molecular-based species delineations was tested on data subsets. Novel phylogenetic and taxonomic results are used for testing and refining earlier hypotheses on the timing and space of pleurobranchoid evolution. Such conclusions will be assessed using massive nuclear ddRADseq-based data in the future. References Bouchet, P. and Rocroi, J.-P. (Ed.); Frýda, J., Hausdorf, B., Ponder, W.F., Valdés, Á. and Warén, A. 2005. Classification and nomenclator of gastropod families. Malacologia 47: 397 pp; ConchBooks: Hackenheim, Germany. Göbbeler, K. and Klussmann-Kolb, A. 2010. Out of Antarctica? New insights into the phylogeny and biogeography of the Pleurobranchomorpha (Mollusca, Gastropoda). Mol. Phylogenet. Evol. 55: 996–1007. Martynov, A.V. and Schrödl, M. 2009. The new Arctic side-gilled sea slug genus Boreoberthella (Gastropoda, Opisthobranchia): Pleurobranchoidean systematics and evolution revisited. Polar Biol 32: 53-70. WoRMS Editorial Board. 2015. World Register of Marine Species. Available from http://www.marinespecies.org at VLIZ. Accessed 2015-06-11. This work was supported by the Russian Foundation for Basic Research (grant 13-04-01641a), the Russian Science Foundation (grant 14-50-00029), DFG (SCHR 667/13), and DFG-1158 (SCHR 667/15-1).