First molecular phylogeny of the subfamily Polycerinae (Mollusca, Nudibranchia, Polyceridae)

Helgoland Marine Research, Mar 2014

The subfamily Polycerinae includes four genera with around 46 species described to date. This subfamily is characterized by a limaciform body, which may have simple tentacular processes on the margin of the oral veil. Phylogenetic relationships between the genera of the subfamily Polycerinae (Polyceridae) have not yet been studied, and therefore, the only available information is based on morphological descriptions. The present study reports the first phylogenetic analysis of Polycerinae based on the mitochondrial genes cytochrome oxidase subunit I and the large ribosomal subunit (16S rRNA) using maximum likelihood and Bayesian methods. Our results showed that Polycerinae is monophyletic, but the relationships within the subfamily as well as within Polycera remain unresolved. A key finding of this study is that there are clearly two sympatric species of Polycera present in South Africa: Polycera capensis Quoy and Gaimard, 1824 also found in Australia and an undescribed Polycera sp. On the other hand, the studied specimens of the genus Gymnodoris were clustered within Polycerinae, reopening the problem of the systematic position of this genus. Additional genes and species of Polycerinae and Gymnodoris would provide more information and probably fully resolve this situation.

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First molecular phylogeny of the subfamily Polycerinae (Mollusca, Nudibranchia, Polyceridae)

Helgol Mar Res First molecular phylogeny of the subfamily Polycerinae (Mollusca, Nudibranchia, Polyceridae) Gemma Palomar 0 1 2 Marta Pola 0 1 2 Eva Garcia-Vazquez 0 1 2 0 M. Pola Departamento de Biolog ́ıa, Universidad Auto ́noma de Madrid, Edificio de Biolog ́ıa, Campus de Excelencia Internacional UAM?CSIC, C/ Darwin , 2, 28049 Madrid , Spain 1 G. Palomar (&) E. Garcia-Vazquez Departamento de Biolog ́ıa Funcional, Universidad de Oviedo , C/ Julian Claveria s/n, 33006 Oviedo , Spain 2 Communicated by H.-D. Franke The subfamily Polycerinae includes four genera with around 46 species described to date. This subfamily is characterized by a limaciform body, which may have simple tentacular processes on the margin of the oral veil. Phylogenetic relationships between the genera of the subfamily Polycerinae (Polyceridae) have not yet been studied, and therefore, the only available information is based on morphological descriptions. The present study reports the first phylogenetic analysis of Polycerinae based on the mitochondrial genes cytochrome oxidase subunit I and the large ribosomal subunit (16S rRNA) using maximum likelihood and Bayesian methods. Our results showed that Polycerinae is monophyletic, but the relationships within the subfamily as well as within Polycera remain unresolved. A key finding of this study is that there are clearly two sympatric species of Polycera present in South Africa: Polycera capensis Quoy and Gaimard, 1824 also found in Australia and an undescribed Polycera sp. On the other hand, the studied specimens of the genus Gymnodoris were clustered within Polycerinae, reopening the problem of the systematic position of this genus. Additional genes and species of Polycerinae and Gymnodoris would provide more information and probably fully resolve this situation. COI; 16S; Gymnodoris; Nudibranchia; Polycerinae; Polycera capensis Introduction The absence of nudibranchs in fossil records has complicated the understanding of their biology and evolution (Valde´s 2001) . Despite this limitation, many studies based on classical morphology have been undertaken since the nineteenth century (e.g., Alder and Hancock 1845–1855; Bergh 1877, 1890, 1902, 1906; Odhner 1934; Valde´s and Gosliner 1999; Wa¨gele and Willan 2000; Valde´s 2001, 2002; Fahey and Gosliner 2001, 2004; Gosliner 2004; Pola et al. 2005a, 2006a) . However, a taxonomy based only on morphology has its limits (Medina and Walsh 2000; Wiens and Penkrot 2002; Fall et al. 2003; Dayrat 2005) . Morphological characters may vary within the same species as the result of selective pressures and adaptation to varying environmental parameters (Wa¨gele 2005), and the choice of taxonomically informative characteristics depends on the criteria of taxonomists (Mikkelsen 1998) . Molecular techniques can palliate these limitations (Medina and Collins 2003; Wa¨gele et al. 2003; Wa¨gele 2005; OrnelasGatdula et al. 2012; Pola et al. 2012; Carmona et al. 2013) . Mitochondrial genes have provided interesting information on the phylogeny of nudibranchs (Tho¨ llesson 1999a, b, 2000; Medina et al. 2001; Wollscheid-Lengeling et al. 2001; Fahey 2003; Valde´s 2003; Wilson and Lee 2005; Pola et al. 2007; Turner and Wilson 2008; Johnson 2010; Pola and Gosliner 2010; Johnson and Gosliner 2012; Carmona et al. 2013) . The results of these researches have clarified the relationships within some groups, but there are still many unclear phylogenetic relationships, for example, within species grouped under the family Polyceridae Alder and Hancock, 1845 (superfamily Polyceroidea, subclade Doridacea, clade Euctenidiacea; Bouchet and Rocroi 2005) . This family includes a group of nudibranchs that have elongate and limaciform bodies and a reduced mantle skirt. Their lamellate rhinophores have a pocket, and sometimes a sheath into which they can retract, although their gills are non-retractile. In the past, it was related to notodorids and gymnodorids. Old classifications included gymnodorids as subfamily Gymnodoridinae within the family Polyceridae (Eliot, 1903) , although other authors such as Odhner (1941) believed they should be regarded as distinct. Macnae (1958) considered that gymnodorids and polycerids shared enough characters to belong to the same family. Both have their principal ganglia concentrated into a compact mass above and alongside the esophagus. Their pleural and cerebral ganglia are usually enclosed in the same sheath and are not easily distinguishable when viewed from above. Their abdominal ganglion is drawn up so as to lie close to the pleural ganglion on the right side. They have a blood gland in association with the anterior aorta, lying in the mass of connective tissue overlying the posterior portion of the anterior genital mass. Only the buccal region and its armature, the form of the radula and its teeth, are different in both families and are used as diagnostic characters even at species level (Macnae 1958) . Nowadays, G (...truncated)


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Gemma Palomar, Marta Pola, Eva Garcia-Vazquez. First molecular phylogeny of the subfamily Polycerinae (Mollusca, Nudibranchia, Polyceridae), Helgoland Marine Research, 2014, pp. 143-153, Volume 68, Issue 1, DOI: 10.1007/s10152-013-0374-z