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Schrodl M.,Mollusca Section | Schrodl M.,Ludwig Maximilians University of Munich | Stoger I.,Mollusca Section
Journal of Natural History | Year: 2014

Molluscs are diverse and important enough to receive considerable scientific attention. We herein question recent opinions that the molluscan origin, deep inner relationships, and early evolution have been largely resolved. The traditional Testaria concept implied progressive evolution from worm-like aplacophoran to polyplacophoran and then conchiferan body plans; sole evidence for this came from morphocladistic analyses, which we conclude were confounded by homoplasy. The recently preferred Aculifera-Conchifera concept is supported by some but not all analyses using massive sequence data on rather small and uneven taxon sets. Recent results from mitogenomics indicate that gene-rearrangement events could cause sequence biases overriding potential phylogenetic signal. We discuss recent progress regarding multilocus marker analyses, particularly refining the neglected Serialia hypothesis with Monoplacophora sister to Polyplacophora. This third hypothesis for molluscan relationships is supported by an integrative interpretation and is roughly compatible with available fossil evidence if the first molluscs were small and had a true shell rather than a chiton-like body organization. Despite some claims of consensus, there are substantial discrepancies among recent molecular studies regarding class-level topologies. These may be symptomatic of a plethora of factors and evolutionary processes – obvious or more hypothetical – that might hinder successful reconstruction of early molluscan diversification. © 2014, © 2014 Taylor & Francis. Source

Nekola J.C.,University of New Mexico | Coles B.F.,Mollusca Section | Horsak M.,Masaryk University
Journal of Molluscan Studies | Year: 2015

Using the Pupilla faunas of Europe, North America, the Altai region of central Asia and eastern Asia, we consider whether the existing taxonomy based primarily on shell apertural characteristics correlates with relationships established on the basis of mitochondrial and nuclear DNA-sequence data. We obtained DNA sequence from nuclear ITS1 and ITS2 and mitochondrial COI and CytB from 80 specimens across 22 putative Pupilla taxa. The sequence data were analysed using maximum likelihood, maximum parsimony, Bayesian and neighbour-joining phylogenetic tree reconstruction, as well as base-pair substitution and insertion-deletion analysis. Revised species-level concepts were generated by identifying reciprocally monophyletic clades that exhibited unique conchological features. These analyses document that, although many previously described taxa have biological merit, the highly plastic nature of shell apertural features makes them unreliable indicators of species identity in several independent lineages. However, shell surface sculpture and architecture appear to provide more reliable diagnoses. Because of the traditional reliance of species-level taxonomy in Pupilla on plastic apertural features, too many species-level entities have been described in Europe and the Altai. Also, because taxonomically useful shell sculpture features have tended to be ignored, too few species have been described in eastern Asia and North America. As a result, confusion exists about species ranges, ecological tolerances and interpretation of Quaternary fossils within the genus. Based on these analyses three new species are described: P. alaskensis, P. hudsonianum and P. hokkaidoensis. © 2014 © The Author 2014. Published by Oxford University Press on behalf of The Malacological Society of London, all rights reserved. Source

Nekola J.C.,University of New Mexico | Coles B.F.,Mollusca Section
American Malacological Bulletin | Year: 2010

The Pupillidae form an important component of eastern North American land snail biodiversity, representing approx. 12% of the entire fauna, 25-75% of all species and individuals at regional scales, at least 30% of the species diversity, and 33% of individuals within any given site. In some regions pupillids represent 80-100% of total molluscan diversity within sites, notably in taiga, tundra, and the base-poor pine savannas and pocosins of the southeastern coastal plain. Adequate documentation of North American land snail biodiversity thus requires investigators to efficiently collect and accurately identify individuals of this group. This paper presents a set of annotated keys to the 65 species in this family known to occur in North America east of the Rocky Mountains. The distinguishing taxonomic features, updated county-scale range maps, and ecological conditions favored by each are presented in hopes of stimulating future research in this important group. Source

Jorger K.M.,Mollusca Section | Jorger K.M.,Ludwig Maximilians University of Munich | Schrodl M.,Mollusca Section | Schrodl M.,Ludwig Maximilians University of Munich
Frontiers in Zoology | Year: 2013

Background: Molecular methods of species delineation are rapidly developing and widely considered as fast and efficient means to discover species and face the 'taxonomic impediment' in times of biodiversity crisis. So far, however, this form of DNA taxonomy frequently remains incomplete, lacking the final step of formal species description, thus enhancing rather than reducing impediments in taxonomy. DNA sequence information contributes valuable diagnostic characters and -at least for cryptic species - could even serve as the backbone of a taxonomic description. To this end solutions for a number of practical problems must be found, including a way in which molecular data can be presented to fulfill the formal requirements every description must meet. Multi-gene barcoding and a combined molecular species delineation approach recently revealed a radiation of at least 12 more or less cryptic species in the marine meiofaunal slug genus Pontohedyle (Acochlidia, Heterobranchia). All identified candidate species are well delimited by a consensus across different methods based on mitochondrial and nuclear markers. Results: The detailed microanatomical redescription of Pontohedyle verrucosa provided in the present paper does not reveal reliable characters for diagnosing even the two major clades identified within the genus on molecular data. We thus characterize three previously valid Pontohedyle species based on four genetic markers (mitochondrial cytochrome c oxidase subunit I, 16S rRNA, nuclear 28S and 18S rRNA) and formally describe nine cryptic new species (P. kepii sp. nov., P. joni sp. nov., P. neridae sp. nov., P. liliae sp. nov., P. wiggi sp. nov., P. wenzli sp. nov., P. peteryalli sp. nov., P. martynovi sp. nov., P. yurihookeri sp. nov.) applying molecular taxonomy, based on diagnostic nucleotides in DNA sequences of the four markers. Due to the minute size of the animals, entire specimens were used for extraction, consequently the holotype is a voucher of extracted DNA ('DNA-type'). We used the Character Attribute Organization System (CAOS) to determine diagnostic nucleotides, explore the dependence on input data and data processing, and aim for maximum traceability in our diagnoses for future research. Challenges, pitfalls and necessary considerations for applied DNA taxonomy are critically evaluated. Conclusions: To describe cryptic species traditional lines of evidence in taxonomy need to be modified. DNA sequence information, for example, could even serve as the backbone of a taxonomic description. The present contribution demonstrates that few adaptations are needed to integrate into traditional taxonomy novel diagnoses based on molecular data. The taxonomic community is encouraged to join the discussion and develop a quality standard for molecular taxonomy, ideally in the form of an automated final step in molecular species delineation procedures. © 2013 Jörger and Schrödl; licensee BioMed Central Ltd. Source

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