A molecular phylogeny of Planorboidea (Gastropoda, Pulmonata): insights from enhanced taxon sampling

Abstract

Planorbid gastropods are the most diverse group of limnic pulmonates, with both discoidal and highspired taxa. Phylogenetic relationships among these genera are confused and controversial. In particular, the monophyly of the limpet‐like taxa (traditionally Ancylidae) is disputed. Even recent molecular studies have concluded that substantially more work is necessary to solve the remaining issues concerning intergeneric phylogenetic relationships and higher taxa systematics. Planorbid snails are of great significance for humans as several members of this group are intermediate hosts of blood flukes (schistosomes) causing a chronic disease, schistosomiasis. We used the two independent molecular markers COI and 18S (concatenated dataset of 2837 nucleotide bp) to infer phylogenetic relationships of 26 genera (27 species) of Planorboidea, represented mostly by type species from mainly topotypical populations. With the majority of the taxa discussed not having been studied previously, this study attempted to test several hypotheses on planorbid phylogenetic relationships using Bayesian inference techniques. The monophyly of Planorboidea (= ‘Ancyloplanorbidae’) is strongly suggested on the basis of our extensive molecular analysis. Besides a distinct Burnupia clade, two major clades were recovered that correspond to family level taxa (traditional Bulinidae and Planorbidae). Considerable rearrangements of suprageneric taxa are evident from the phylogeny inferred. Therefore, the only clades recognized by current classifications and supported by our analysis are Planorbini and Segmentinini. The present study found that Ancylidae as traditionally understood, i.e. covering most freshwater limpet gastropods, is paraphyletic, as the genera of Burnupia and Protancylus have been shown to lie phylogenetically outside the Ancylini. Chromosome numbers and levels of polyploidy are discussed in the light of the new phylogeny. An earlier theory of shell shape evolution, i.e. that of patelliform taxa being most advanced, was not supported by this study; a limpet‐shaped taxon is most basal within Planorboidea. Although many taxa still remain to be studied, our results will hopefully contribute towards a better understanding of this very important group of freshwater organisms. Some taxonomic implications are discussed.

Phylogenetic relationships and evolution of pulmonate gastropods (Mollusca): New insights from increased taxon sampling

“…That former ancylids (here Laevepex and Ancylus) are nested within Planorbidae was suggested long ago by Pelseneer (1897) and has been documented by extensive molecular data (Morgan et al, 2002;Jørgensen et al, 2004;Walther et al, 2006;Albrecht et al, 2007). The monophyly of Physidae (e.g., Wethington and Lydeard, 2007), Lymnaeidae (e.g., Remigio and Blair, 1997;Puslednik et al, 2009), Acroloxidae (e.g., Walther et al, 2006) is recovered here with the highest support.…”

Freshwater mollusks and environmental assessment of Guandu River, Rio de Janeiro, Brazil

“…The classification above genus level followed Bouchet & Rocroi (2005), Simone (2006) and Albrecht et al (2007) for the gastropods and Graf & Cummings (2006) and Bieler et al (2010) for bivalves. The mollusks collected were housed at Mollusk Collection of Universidade do Estado do Rio de Janeiro (UERJ).…”

A Middle Miocene endemic freshwater mollusc assemblage from an intramontane Alpine lake (Aflenz Basin, Eastern Alps, Austria)

“…The systematic arrangement follows largely Rocroi (2005, 2010), whilst Albrecht et al (2007) and Jörger et al (2010) are considered for pulmonates and Glöer (2002) for the Emmericiidae. All specimens are stored in the collection of the Geological-Palaeontological Department of the Natural History Museum in Vienna.…”