Polycladida phylogeny and evolution: integrating evidence from 28S rDNA and morphology
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ORIGINAL ARTICLE
Polycladida phylogeny and evolution: integrating evidence from 28S rDNA and morphology Juliana Bahia 1,2
&
Vinicius Padula 3 & Michael Schrödl 1,2
Received: 29 August 2016 / Accepted: 12 December 2016 # Gesellschaft für Biologische Systematik 2017
Abstract Polyclad flatworms have a troubled classification history, with two contradicting systems in use. They both rely on a ventral adhesive structure to define the suborders Acotylea and Cotylea, but superfamilies were defined according to eyespot arrangement (Prudhoe’s system) or prostatic vesicle characters (Faubel’s system). Molecular data available cover a very limited part of the known polyclad family diversity and have not allowed testing morphology-based classification systems on Polycladida yet. We thus sampled a suitable marker, partial 28S ribosomal DNA (rDNA), from Polycladida (19 families and 32 genera), generating 136 new sequences and the first comprehensive genetic dataset on polyclads. Our maximum likelihood (ML) analyses recovered Polycladida, but the traditional suborders were not monophyletic, as the supposedly acotyleans Cestoplana and Theama were nested within Cotylea; we suggest that these genera should be included in Cotylea. The partial 28S rDNA trees were generally well supported and robust but in conflict with both Faubel’s and Prudhoe’s superfamilies. Therefore, we compiled morphological and anatomical characters for all taxa used and examined their distribution on our molecular tree. Electronic supplementary material The online version of this article (doi:10.1007/s13127-017-0327-5) contains supplementary material, which is available to authorized users. * Juliana Bahia [email protected]
1
SNSB-Zoologische Staatssammlung München, Münchhausenstrasse 21, 81247 Munich, Germany
2
GeoBioCenter LMU and Biozentrum of the Ludwig-Maximilians Universität München, Munich, Germany
3
Department of Marine Biotecnology, Instituto de Estudos do Mar Almirante Paulo Moreira (IEAPM), Arraial do Cabo, Brazil
Combining morphological and molecular evidence, we redefined polyclad superfamilies. Acotylea contain tentaculated and atentaculated groups and is now divided in three superfamilies. The suborder Cotylea can be divided in five superfamilies. In general, there is a trait of anteriorization of sensory structures, from the plesiomorphic acotylean body plan to the cotylean gross morphology. Traditionally used characters, such as prostatic vesicle, eyespot distribution, and type of pharynx, are all homoplastic and likely have misled polyclad systematics so far. Keywords Platyhelminthes . Marine flatworms . Cotylea . Acotylea . Molecular phylogenetics . Morphology
Introduction Polycladida are free-living Platyhelminthes that inhabit marine environments, as different as coral reefs, rocky shores, soft bottoms, and deepwater (Newman and Cannon 2003; Quiroga et al. 2006) as also artificial aquaculture structures (Bahia 2015). Around 1000 species of Polycladida are known in the world (Rawlinson 2008; Tyler et al. 2016). The main charac
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