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)