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Polycladida biodiversity and systematics: an integrative approach
Polycladida biodiversity and systematics: an integrative approach
In face of the fact that marine biodiversity is highly threatened by human impacts on the environment, it is important to know what we want to protect. This thesis addresses the biodiversity and systematics of Polycladida, which are free-living Platyhelminthes with highly ramified intestine. Polylclads live in all types of marine environments whereas most areas of the world remain unsampled. From the around 1000 species considered valid many were described based on single or immature specimens and few have designated type material or specimens deposited in museums or research institutions. This is especially the case for Brazilian species that had no type material designated, labeled with codes in the publication or deposited. Characters used traditionally in polyclad taxonomy concern eyespots, type of pharynx, reproductive system, especially prostatic vesicle, but so far, those characters have not been tested against molecular evidence. The order Polycladida has two suborders, Cotylea and Acotylea, and their systematics is based on two conflictive classifications in use, which reflects inadequacy in characters choice. Molecular data from this group is still scarce and there is no morphological or molecular phylogeny that includes the whole order. Three gaps in knowledge are addressed in this work: biodiversity, type material and phylogeny with character evolution. Here I contribute to fill the first one by describing some new species, and by adding novel information, such as color photographs of living animals and microscopic observations to species that are already known. Samplings were made in some previously non-assessed areas in Brazil, Senegal and Cape Verde. One new species from each area is described and distribution ranges are discussed. The genus of the African species Pseudobiceros wirtzi is revised based on literature records. Additionally species associated to aquaculture were sampled for the first time in Brazil. To fill the second gap I studied species from Brazil described by Ernst Marcus and / or Eveline Du Bois-Reymond Marcus. Specimens donated by Eveline Marcus to the Swedish Museum of Natural History were analyzed and I recognized holotypes, paratypes, and designated lectotypes and paralectotypes, as required. Before this work began, most Brazilian species had unknown type material, whereas in this work type specimens of 52 species were designated or recognized. Out the 71 species reported from Brazil, ten remain without information about type material. 4 As a way to fill the third gap I present here a new and comprehensive set of partial 28S nuclear ribosomal DNA (rDNA) data across Polycladida families. Our phylogenetic analysis, despite being based only on a single molecular marker, is the first to test traditional morphology-based hypotheses on relationships inside the order. Remarkably, all our molecular trees were fully resolved and most nodes robustly supported. The overall topology is consistent with evidences from an updated and revised list of morphological and histological characters. Albeit largely congruent at genus and family level, our integrative phylogenetic hypothesis is not compatible with superfamilies and suborders of neither of the two conventional yet conflicting classification systems by Faubel and Prudhoe. The suborders Acotylea and Cotylea, as traditionally considered, were rejected in the hypothesis tests, thus the taxa were amended to reflect molecular monophyly. According to our trees, just two of Prudhoe’s and Faubel’s superfamilies were monophyletic; a novel concept of polyclad superfamily was thus proposed. Molecular results revealed that prominent characters used in previous classifications, such as the position of eyespots, the type of pharynx, and the type of prostatic vesicles were prone to homoplasy in both the Acotylea and the Cotylea branches. A novel scenario of morphological character evolution is suggested and the significance of certain features for taxonomy is discussed. Overall, samples from areas not previously sampled resulted in several new records for Brazil and two new species in this thesis, indicating the potential for future biodiversity exploration. The re-discovery of Ernst and Eveline Marcus’ type material is very important for both the contemporary and future study of Atlantic Polycladida. Our molecular results and its combination to morphological data is a unique effort in Polycladida phylogeny. Even though they are preliminary, the novel hypotheses and the data presented here provide a fresh baseline for future studies on Polycladida systematics.
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Bahia Maceira, Juliana
2017
English
Universitätsbibliothek der Ludwig-Maximilians-Universität München
Bahia Maceira, Juliana (2017): Polycladida biodiversity and systematics: an integrative approach. Dissertation, LMU München: Faculty of Biology
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Abstract

In face of the fact that marine biodiversity is highly threatened by human impacts on the environment, it is important to know what we want to protect. This thesis addresses the biodiversity and systematics of Polycladida, which are free-living Platyhelminthes with highly ramified intestine. Polylclads live in all types of marine environments whereas most areas of the world remain unsampled. From the around 1000 species considered valid many were described based on single or immature specimens and few have designated type material or specimens deposited in museums or research institutions. This is especially the case for Brazilian species that had no type material designated, labeled with codes in the publication or deposited. Characters used traditionally in polyclad taxonomy concern eyespots, type of pharynx, reproductive system, especially prostatic vesicle, but so far, those characters have not been tested against molecular evidence. The order Polycladida has two suborders, Cotylea and Acotylea, and their systematics is based on two conflictive classifications in use, which reflects inadequacy in characters choice. Molecular data from this group is still scarce and there is no morphological or molecular phylogeny that includes the whole order. Three gaps in knowledge are addressed in this work: biodiversity, type material and phylogeny with character evolution. Here I contribute to fill the first one by describing some new species, and by adding novel information, such as color photographs of living animals and microscopic observations to species that are already known. Samplings were made in some previously non-assessed areas in Brazil, Senegal and Cape Verde. One new species from each area is described and distribution ranges are discussed. The genus of the African species Pseudobiceros wirtzi is revised based on literature records. Additionally species associated to aquaculture were sampled for the first time in Brazil. To fill the second gap I studied species from Brazil described by Ernst Marcus and / or Eveline Du Bois-Reymond Marcus. Specimens donated by Eveline Marcus to the Swedish Museum of Natural History were analyzed and I recognized holotypes, paratypes, and designated lectotypes and paralectotypes, as required. Before this work began, most Brazilian species had unknown type material, whereas in this work type specimens of 52 species were designated or recognized. Out the 71 species reported from Brazil, ten remain without information about type material. 4 As a way to fill the third gap I present here a new and comprehensive set of partial 28S nuclear ribosomal DNA (rDNA) data across Polycladida families. Our phylogenetic analysis, despite being based only on a single molecular marker, is the first to test traditional morphology-based hypotheses on relationships inside the order. Remarkably, all our molecular trees were fully resolved and most nodes robustly supported. The overall topology is consistent with evidences from an updated and revised list of morphological and histological characters. Albeit largely congruent at genus and family level, our integrative phylogenetic hypothesis is not compatible with superfamilies and suborders of neither of the two conventional yet conflicting classification systems by Faubel and Prudhoe. The suborders Acotylea and Cotylea, as traditionally considered, were rejected in the hypothesis tests, thus the taxa were amended to reflect molecular monophyly. According to our trees, just two of Prudhoe’s and Faubel’s superfamilies were monophyletic; a novel concept of polyclad superfamily was thus proposed. Molecular results revealed that prominent characters used in previous classifications, such as the position of eyespots, the type of pharynx, and the type of prostatic vesicles were prone to homoplasy in both the Acotylea and the Cotylea branches. A novel scenario of morphological character evolution is suggested and the significance of certain features for taxonomy is discussed. Overall, samples from areas not previously sampled resulted in several new records for Brazil and two new species in this thesis, indicating the potential for future biodiversity exploration. The re-discovery of Ernst and Eveline Marcus’ type material is very important for both the contemporary and future study of Atlantic Polycladida. Our molecular results and its combination to morphological data is a unique effort in Polycladida phylogeny. Even though they are preliminary, the novel hypotheses and the data presented here provide a fresh baseline for future studies on Polycladida systematics.